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4.3 Vin X Hard cold start

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Old 11-29-2009, 06:46 PM   #1
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4.3 Vin X Hard cold start

I'm in the middle of an LT1 rebuild and install, but I want the 4.3 running well when I sell it.

It's a 1996 Vin X 4.3L (the non-Vortec), with an RPO code LF6. When the truck sits overnight, it is very difficult to start. With a good starting circuit and multiple crank overs, the engine won't start until I crank it 6-8 times. Once the engine has run for 30 seconds or more, I can shut it down and refire it without a problem.

Since it's only a problem with a cold motor, I don't think it's the fuel pump.

I've replaced the fuel filter, and have just finished cleaning out the EGR and replacing both the ECT and CTS (both of the coolant temp sensors; one is on the drivers side near the exhaust manifold and the other is on the front of the motor by the EGR; one is grounded through the block, the other has a 2 terminal connector).

I've got a replacement fuel pressure regulator, but don't want to tear the entire top off the engine unless I have to.

So, any thoughts? Do I go with the FPR, or should I look elsewhere first?

Thanks in advance.
Old 11-29-2009, 07:48 PM   #2
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Re: 4.3 Vin X Hard cold start

The FPR could be leaking over the course of a couple hours (over night) and flooding the intake. This usually just causes a bit of a rough start. I don't think this is your problem, though. The fuel pump itself seems to be fine, like you said, but it still may have a problem. The fuel pump has a built-in valve that keeps the fuel system primed with pressure, and it has probably failed. As the truck sits, the fuel system leaks it's pressurized fuel back in to the tank. When you crank the engine, it's like you have just replaced the fuel filter or pump and it has to build up fuel pressure in the system before it can squeeze it through the injectors. After the truck has sat for a few hours or over night, turn the key to "ON" (not all the way to start) for about 3 seconds, then turn it all the way "OFF" (as you would if you wanted to remove the key). Repeat this once or twice more. Then, turn the key as you normally would to start the engine. If it starts much quicker, then you need to change your fuel pump because this valve is built in and not serviceable. Or, you could just do the "key on/key off" trick every time you go to start the truck. Sometimes, it may stumble a bit when the engine fires up. On a side note, my '02 has been doing this for about 3 years now. I usually just do the key on/key off trick once and it starts. It's a pain to drop the tank since it's lowered so much, and I only drive it on the weekends, so I'm not in a rush to fix it right now.
Old 11-29-2009, 08:00 PM   #3
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Re: 4.3 Vin X Hard cold start

Before replacing the FPR, make sure that the fuel pump primer relay is working propperly. When you turn the key to run the primer relay needs to kick on for at least 3 full seconds. A lot of the relays will get sticky and take a second or so to kick on.
There is a fuel pump test lead on the pass side fire wall. You can connect a test light to it. The test lead will have +12v when the pump has + 12v. If you apply + 12volts to that wire the pump will run.

If the relay works well and the ground on the pump is good then testing the fuel preassure and bleed down time, then replacing the FPR is the next simple step.
Old 11-29-2009, 09:46 PM   #4
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Re: 4.3 Vin X Hard cold start

95 was the last year for the TBI and the CPI, the 96 should have Vortec heads. I would suspect the priming relay first, it can be swapped with a different relay....
Old 11-30-2009, 03:51 PM   #5
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Re: 4.3 Vin X Hard cold start

Sorry, I should have included that. Fuel pump prime works great, spins for 2-3 seconds when I turn the key on. If I turn it off and then back on immediately, I don't get any priming, but if I leave the key off for 5-10 seconds, it'll prime again. This SOMETIMES, MARGINALLY helps, but not a significant amount recently. And it seems to be worse than it was last summer.

Lesterl, I definitely don't have the Vortec heads; I'm pretty sure I've got the CSEFI setup. It seems to be somewhat rare. Third one down, and of course, the one without the picture:
http://forums.s-series.org/viewtopic.php?f=13&t=12717

So...how do I decide whether it's the leak-by valve in the fuel pump or the FPR?
Old 11-30-2009, 09:06 PM   #6
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Re: 4.3 Vin X Hard cold start

Quote: Originally Posted by D.Snutz
Sorry, I should have included that. Fuel pump prime works great, spins for 2-3 seconds when I turn the key on. If I turn it off and then back on immediately, I don't get any priming, but if I leave the key off for 5-10 seconds, it'll prime again. This SOMETIMES, MARGINALLY helps, but not a significant amount recently. And it seems to be worse than it was last summer.

Lesterl, I definitely don't have the Vortec heads; I'm pretty sure I've got the CSEFI setup. It seems to be somewhat rare. Third one down, and of course, the one without the picture:
http://forums.s-series.org/viewtopic.php?f=13&t=12717

So...how do I decide whether it's the leak-by valve in the fuel pump or the FPR?
1996-2003 was CSFI IIRC. They do use the higher flowing Vortec heads CSFI was all that was available durring the years listed, after 2003 they went to MPFI. There is a kit available for the 1996-2003 to convert to the MPFI.

The delay in priming is programmed in, you need to cycle the power several times, might try to start it with another vehicle hooked up as jump start of your vehicle to boost the battery voltage to 14.4Vdc which will spin the pump faster and thus increase pressure, if it starts better, you can then suspect the pump, might throw a fuel pressure guage on it to see what it is at and if it bleeds off.
Old 11-30-2009, 09:55 PM   #7
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Re: 4.3 Vin X Hard cold start

Then I say; replace the FPR.
Old 12-01-2009, 10:42 AM   #8
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Re: 4.3 Vin X Hard cold start

Quote: Originally Posted by lesterl
1996-2003 was CSFI IIRC. They do use the higher flowing Vortec heads CSFI was all that was available durring the years listed, after 2003 they went to MPFI. There is a kit available for the 1996-2003 to convert to the MPFI.

The delay in priming is programmed in, you need to cycle the power several times, might try to start it with another vehicle hooked up as jump start of your vehicle to boost the battery voltage to 14.4Vdc which will spin the pump faster and thus increase pressure, if it starts better, you can then suspect the pump, might throw a fuel pressure guage on it to see what it is at and if it bleeds off.

Lesterl, thanks for the head lesson. No wait, that didn't come out right...

Anyway, I've never quite figured out this VIN X, it seems to be a bit of a bastard configuration. So the VORTEC heads were available and worked with the TBI-appearing intake manifold? I don't have the LT1-imitation crossover intake runner upper intake, just a top mounted TB.

I guess it's not really that important; the FPR is still inside the upper intake assembly. I'm pretty sure it's not the fuel pump, since I don't get any lean running issues, even at high RPM.

Even with priming four or five times, the vehicle is still hard to start. I suppose it's still possible for it to be the supply line check valve in the fuel pump assembly. Do you know of a check valve I could install, say, near the fuel filter at the frame rail that would do the same thing and would be easier to deal with than dropping the tank?

I'm really leaning toward the FPR, I'm just whining about having to pull the manifold off. Cleaning and gaskets and all the sensors and blargh. I've considered buying a fuel pressure gauge (auto parts store doesn't rent them here), but if it leaks down, that still won't indicate whether it's the fuel pump check valve or the FPR (down through the supply line, or down through the FI return line...does it matter?).

Then again, I'll probably have to go to a higher flow pump when I get the LT1 in, so maybe I should start there? But that's a REAL pain to do.
Old 12-01-2009, 09:26 PM   #9
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Re: 4.3 Vin X Hard cold start

Quote: Originally Posted by D.Snutz
...Do you know of a check valve I could install, say, near the fuel filter at the frame rail that would do the same thing and would be easier to deal with than dropping the tank?
Hmmm. I never thought about that. I'm now wondering the same.

Quote: Originally Posted by D.Snutz
I'm really leaning toward the FPR, I'm just whining about having to pull the manifold off. Cleaning and gaskets and all the sensors and blargh. I've considered buying a fuel pressure gauge (auto parts store doesn't rent them here), but if it leaks down, that still won't indicate whether it's the fuel pump check valve or the FPR (down through the supply line, or down through the FI return line...does it matter?).

Then again, I'll probably have to go to a higher flow pump when I get the LT1 in, so maybe I should start there? But that's a REAL pain to do.
Opening up the intake manifold is a pain, but I'd say dropping the tank is a bit less of a pain. At least, it is for me since I've done it 3 times on my lowered Xtreme. If you don't have a sprayed-in liner, remove the bed bolts and slide the bed back to get to the top of the tank.
Old 12-03-2009, 05:24 PM   #10
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Re: 4.3 Vin X Hard cold start

xtremist, I started on pulling the intake manifold. Not because I don't value your input or opinion, but because I'm a stubborn fool.

Turns out it cannot be done without a 10mm deepwell. I picked one up last night. I hope to finish it up this weekend, but we'll see. I'll be sure to post up what I find out, along with pictures.

Holy crap, I hope I can figure out where all those electrical connectors go. Two to the alternator, two to the IAC & TPS, the fuel meter body of course, the two throttle/cruise cables, EGR, EVAP... I guess I'm stubborn and also too impatient to label stuff like I should have. DOH!
Old 12-03-2009, 09:26 PM   #11
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Re: 4.3 Vin X Hard cold start

I guess you could have pulled the 3 bolts holding on the Throttle body and looked down inside.
Old 12-03-2009, 10:07 PM   #12
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Re: 4.3 Vin X Hard cold start

Quote: Originally Posted by D.Snutz
xtremist, I started on pulling the intake manifold. Not because I don't value your input or opinion, but because I'm a stubborn fool.
Hey man, you're not gonna offend me. I'm just sharing my experiences with similar symptoms in hopes that it'll help you get this problem whupped. (Yes, I meant to say "whupped"!)

Quote: Originally Posted by D.Snutz
...I'll be sure to post up what I find out, along with pictures.
Do that. I, for one, am definitely interested.
Old 12-04-2009, 12:28 PM   #13
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Re: 4.3 Vin X Hard cold start

PIDDERS!!!







Those are all taken from my LT1 rebuild blog; some unrelated pics are also up there on the LT1, the Bourbon resurrection, and the Sopping Stratus.

I'll get back to this next week. Tonight is the Nutcracker with the girl, and I've got a reserve weekend Sat & Sun. I did pick up the deepwell, so that's a small step.
Old 12-04-2009, 05:00 PM   #14
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Re: 4.3 Vin X Hard cold start

The FPR is in the top of the TBI, and only takes a few minutes to replace. I think it runs about $18 - $25 with all the gaskets.
Old 12-04-2009, 06:25 PM   #15
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Re: 4.3 Vin X Hard cold start

Quote: Originally Posted by D.Snutz
...Tonight is the Nutcracker with the girl...
Damn, let's keep your freak sex life out of this and stay on subject!
Old 12-04-2009, 08:38 PM   #16
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Re: 4.3 Vin X Hard cold start

Coil looks aftermarket as well....
Old 12-10-2009, 01:44 AM   #17
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Re: 4.3 Vin X Hard cold start

xtremist-- SHADDUP...dat's nunya foo!

Lester: Right on; ACCEL tune up kit. First thing that went on, right after the exhaust came off.

SOOOOoooo....I got the new FPR in there. Pictures below. When I reinstalled the Upper Intake Manifold (UIM?), I ripped up the seal around the fuel meter body. She fired up, but it took a good ten or fifteen cranks. No improvement, and now the idle was HORRIBLE...hunting up and all most all the way down to a stall, followed by a huge gasp, and then it'd fire back up. So I knew something was wrong.

So tonight, I ripped it ALL back off again, and there was a bunch of seal PIECES lying in the intake runners. Crap. I fished everything out, but it didn't make a full oval. I'm hoping everything else either flies through or is chopped up...I was only missing about 1/8" of seal. I HOPE???

Ran to O'Reilley's, got a FelPro kit. Yes, it was thirty bucks vice the 10 I probably could have spent, but I got a TB gasket and a UIM gasket and tossed those in as well. Got it all put back together.

I only primed it twice, and it tried to turn over on the first turn. It didn't quite make until the fourth crank, but it fired right up and idled smoothly! Granted, I had run it for a minute or so earlier in the evening, but I'd also relieved the fuel pressure from pulling the fuel lines. So, I'm not 100% sure, but I feel a LOT better about it than I have in a couple months! We'll see tomorrow. Keep you guys updated!







Nom nom nom....rebuild fuel:




Last edited by D.Snutz; 12-10-2009 at 01:47 AM.
Old 12-12-2009, 02:48 PM   #18
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Re: 4.3 Vin X Hard cold start

Congrats (I think/hope)!
Old 12-14-2009, 01:03 PM   #19
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Re: 4.3 Vin X Hard cold start

Quote: Originally Posted by s10xtremist
Congrats (I think/hope)!
Fired her up yesterday, and it was still a bit difficult of a start. Four or five cranks. ALTHOUGH, I still hadn't run it any distance, just idled in the garage. I got her out and drove her for about half an hour yesterday (and found the radiator fan electrical problem, FINALLY--stupid installer didn't know what the hell they were...crap, that's me). Sat for three hours, and fired right up to move it back into the garage. It's been sitting overnight; I'll try it this evening when I get home.

After the (lesser) trouble starting yesterday, I may have to listen to your voices of reason and pull the pump.

Is there a wahlbro or other aftermarket option for an S10? Summit just has OEM replacements. I think I'll eventually need more flow for the LT1 if I decide to put in a blower or nitrous. Any suggestions if I go that route? How much flow? 55gph or more?
Old 12-14-2009, 08:20 PM   #20
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Re: 4.3 Vin X Hard cold start

I had a Walbro 255 in mine for a little while. It's slightly larger in diameter than the stock pump, so it's a really tight squeeze to fit it into the rubber isolators. Other than that, it's a direct plug-and-play swap. Also, if the one you get is in a kit that comes with it's own piece of "EFI" rated fuel line, don't use it. Reattach your stock "umbilical cord" fuel hose. I installed my Walbro and it worked great until that "EFI" rated hose that came with it in the kit deteriorated inside my gas tank and clogged up my filter and pump. I don't have any model numbers, but a quick search here or on Google should find you something, as this is a common swap.
Old 12-15-2009, 10:19 AM   #21
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Re: 4.3 Vin X Hard cold start

xtrem, thanks for the info. I'll take a look. I had battery voltage problems last night; it's on the slow charger now. We'll see tonight.

I'm also fighting a vacuum control problem on my 6.5L TD in the suburban, so when I get pissed off at one, I go fight the other one.
Old 12-17-2009, 10:50 AM   #22
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Re: 4.3 Vin X Hard cold start

With a full battery charge, it fires on the third or fourth start, so that's MANY times better than the 15 or 20 I was doing, so it's definitely better! I'll still probably replace the fuel pump, but it's definitely drivable now! Thanks to all of you, and I'll keep you up to date with both the pump and the LT1...
Old 12-26-2009, 12:15 AM   #23
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Re: 4.3 Vin X Hard cold start

Quote: Originally Posted by D.Snutz
With a full battery charge, it fires on the third or fourth start, so that's MANY times better than the 15 or 20 I was doing, so it's definitely better! I'll still probably replace the fuel pump, but it's definitely drivable now! Thanks to all of you, and I'll keep you up to date with both the pump and the LT1...
I think you likely have a leak in the pulsator/valve on the fuel pump. I has a similar issue and pulled the thing off and replaced it with fuel line. No start up issues after that. 1 crank and all good. You really should test the fuel pressure at the test valve under the hood to be sure you have a leak.

Good luck and please let us know.
A.

Last edited by neex; 12-26-2009 at 12:23 AM.
Old 12-28-2009, 07:53 PM   #24
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Re: 4.3 Vin X Hard cold start

I grabbed my dad's fuel pressure gauge while I was home for Christmas, but sadly, I couldn't fit it in the luggage on the way back. It's getting mailed to me as we speak, but it'll be a few days yet.

If I'm pulling the bed to get to the fuel pump, I'm replacing the whole stupid thing.
Old 01-04-2010, 05:57 PM   #25
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Re: 4.3 Vin X Hard cold start

Fuel pressure last night was a steady 52 lbs with the key on. It would drift down to 50 with the key off, but then became static. I don't know what the pressure was with the engine running or cranking, since i was checking it by myself last night.

So...are we still thinking fuel pump/pulsator?
Old 01-04-2010, 06:02 PM   #26
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Re: 4.3 Vin X Hard cold start

Myeh... I always thought it needed around 60 PSI, no less than 55 with it running.
Old 01-05-2010, 02:14 PM   #27
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Re: 4.3 Vin X Hard cold start

Quote: Originally Posted by s10xtremist
Myeh... I always thought it needed around 60 PSI, no less than 55 with it running.
Walbro from APE, FPG003:
http://www.autoperformanceengineerin...s.html#gm_apps

Racetronix:
http://www.racetronix.biz/customkiti...c=RFPK-003&eq=

Which do you guys like? If the Racetronix, do you have a recommended model?
Old 01-07-2010, 10:26 AM   #28
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Re: 4.3 Vin X Hard cold start

Vas is dis??? A place on the internet that DOESN'T have an opinion on something?? WOW
Old 01-14-2010, 02:44 PM   #29
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Re: 4.3 Vin X Hard cold start

Last night, I got to work on this (and the LT1) a little bit. The truck was much easier to start last night for some reason. I had a voltmeter hooked up to the battery to watch it and the fuel pressure gauge on the fuel rail. The battery isn't the strongest thing, or so I thought, but it was at 12.5 with just the multimeter on. As I cranked it, I saw voltage drop to somewhere around 9.5-10.5 volts during cranking, and then come back up to around 12, before creeping back to 12.5. I know this TREND is normal, but are the actual values what you'd expect? All the way to 10V? On the suspicion that the fuel pump was starving for power, I took the battery down to the autoparts store for testing. It checked out fine, although low. When I came back, fuel pressure (I hadn't disturbed it) had dropped from 58lbs down to around 48 or 50, and it continued to slowly drop (that reading was at least an hour later).

The ODD thing was that the engine fired after only 3 or 4 attempts again, much like the last time I had the fuel pressure gauge installed. THIS seems to indicate that the motor is starving for fuel, but the added volume of the gauge line supplies sufficient fuel to fire the motor. Granted, coincidence does not imply causation, but it's a reasonable theory, right?

If this is the case, do you think it's a fuel pump exhaustion issue? Oh, I'm still looking to buy a Racetronix pump, but I don't know which model to get. Any opinions there?
Old 01-14-2010, 10:04 PM   #30
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Re: 4.3 Vin X Hard cold start

I still think your fuel pump is messed up. I don't know which Racetronix kit to suggest, have you tried calling them? Our 4.3s are basically the same as the LT-series engines, so a pump for an LT1 V8 should be just fine for the V6.
Old 01-14-2010, 10:54 PM   #31
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Re: 4.3 Vin X Hard cold start

Voltages seem fine. The 10v drop when cranking is due to the enormus current draw by the starter, that is why the fuel system gets "primed"
Old 01-14-2010, 11:02 PM   #32
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Re: 4.3 Vin X Hard cold start

lesterl, I thought so as well. Like xtremist said, gotta be the fuel pump, I guess.

I'd call Racetronix, but they don't publish a phone number that I could find. I know the similarity of the motors; what I'm more worried about is the fuel tank compatibility. I guess I'll just get the F Body pump kit and hope for the best...
Old 01-14-2010, 11:16 PM   #33
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Re: 4.3 Vin X Hard cold start

I had an F-body fuel pump in my Xtreme. I don't think the tank matters since the pump mounts in a bucket. I guess they change the bucket design to fit whatever tank it's going in, but the pump itself remains the same.
Old 01-15-2010, 11:20 AM   #34
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Re: 4.3 Vin X Hard cold start

Okay! I've got a manual boost controller on the way for the suburban to fix the wastegate problem; once it's here, I'll order the pump.

Pictures and updates when it gets here...
Old 01-31-2010, 12:57 AM   #35
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Re: 4.3 Vin X Hard cold start

Quote: Originally Posted by D.Snutz

Even with priming four or five times, the vehicle is still hard to start....
Try replacing the CTS. If the CTS is lazy, it will starve the motor of fuel when cold and do the reverse when warm. Does it run a little rich when warm (i.e. fuel milage taking a bit of a dive?). Lazy CTS situations won't throw codes and almost always cause a SOB start situation. You might try replacing it...

Good luck.
A.
Old 01-31-2010, 09:06 AM   #36
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Re: 4.3 Vin X Hard cold start

Quote: Originally Posted by neex
Try replacing the CTS. If the CTS is lazy, it will starve the motor of fuel when cold and do the reverse when warm. Does it run a little rich when warm (i.e. fuel milage taking a bit of a dive?). Lazy CTS situations won't throw codes and almost always cause a SOB start situation. You might try replacing it...

Good luck.
A.
What's the "CTS"? And by "SOB start situation", is "SOB" another abbreviated technical term or is it "son of a bitch"?
Old 02-01-2010, 01:34 PM   #37
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Re: 4.3 Vin X Hard cold start

I've replaced both the CTS (coolant temp sensor) and the other one...ECT? One is single terminal/ground to the block, the other is a 2 wire connector with return path. Whatever...one goes to the computer, the other to the gauge. Of course, the one that goes to the gauge had a different resistance range, so normal operating temperature with teh thermostat open was almost in the red zone. Scared me at first, but then I boiled them in water together and took some resistance measurements, and saw the difference in res. Regardless, the new sensors didn't help.

Racetronix F-body LT1 pump is on the way. I'll update when I get it in.
Old 03-23-2010, 01:30 AM   #38
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Re: 4.3 Vin X Hard cold start

FINALLY, an update. After skiing Whitefish, and the g/f's brother coming to town, and going to the winter Olympics, and excuses and BS and stuff, I finally got the Racetronix/Walhbro FLT-1 installed. It fired on the first shot, no issues whatsoever. Primed fuel pressure was over 65, maybe over 70 lbs, and the truck started faster (fewer revolutions on the starter) than it ever has before. SO...if anyone ever reads this junk in the future, don't bother with the fuel pressure regulator, and go straight for the fuel pump.

Hey Xtremist, if it matters to you: YOU WERE RIGHT! hahahaha

Thanks all for the help. Moving on to the LT1 again...
Old 03-23-2010, 02:40 AM   #39
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Re: 4.3 Vin X Hard cold start

nice man, i just read the whole thread since i think im having fuel pump issues...congrats!
Old 03-23-2010, 08:49 PM   #40
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Re: 4.3 Vin X Hard cold start

Quote: Originally Posted by D.Snutz
xtremist, I started on pulling the intake manifold. Not because I don't value your input or opinion, but because I'm a stubborn fool.
Damned hard-headed kids these days- if only they would put down the Powder Hound for two minutes and listen, they might learn something...
*end Foghorn Leghorn moment*

Glad you got it fixed! I'm keeping my fingers crossed that this actually was the solution and not just a fluke. I still need to change the pump in my '02 and I'm considering the FLT-1. When you got it, is that all it was- a reboxed Walbro 255? How'd the install go? How much was it?
Old 05-15-2010, 10:19 AM   #41
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Re: 4.3 Vin X Hard cold start

All no start situations seem to be easy fixed but cons of bitches to get there.



A.

Quote: Originally Posted by neex
Try replacing the CTS. If the CTS is lazy, it will starve the motor of fuel when cold and do the reverse when warm. Does it run a little rich when warm (i.e. fuel milage taking a bit of a dive?). Lazy CTS situations won't throw codes and almost always cause a SOB start situation. You might try replacing it...

Good luck.
A.
Old 05-15-2010, 03:42 PM   #42
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Re: 4.3 Vin X Hard cold start

Is all that it takes is propper troubleshooting techniques, a little common sense and least as possible knuckle grinding.
Just because a new fuel pump fixed someones issue, doesn't mean that it will fix your problem if your pump is good.

Good luck.
Old 10-21-2010, 06:04 PM   #43
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Re: 4.3 Vin X Hard cold start

Quote: Originally Posted by s10xtremist
Damned hard-headed kids these days- if only they would put down the Powder Hound for two minutes and listen, they might learn something...
*end Foghorn Leghorn moment*

Glad you got it fixed! I'm keeping my fingers crossed that this actually was the solution and not just a fluke. I still need to change the pump in my '02 and I'm considering the FLT-1. When you got it, is that all it was- a reboxed Walbro 255? How'd the install go? How much was it?

Sorry, I wasn't paying attention when I read this earlier. Truck is still running great, although I'll be taking it down next month to start the LT1 swap, assuming the rest of the wiring and such goes (relatively) well with the build.

Yes, it was just a Walhbro. It had a new screen and the electrical connection in it, but I think that was it. I did end up buying an Airtek pump and basket, since I brokededed mine--and then I had to meld the two. But it's running great now. I have had an intermittent small evap leak engine code that I suspect has to do with the fuel line connections or O-ring seal on the take. I get the light every 600 or 900 miles (2 or 3 tanks of fuel), and it goes out on its own after 20 or 40 miles. It might be the gas cap, it might have been the fuel pump install; hard to say.

Again, sorry it took so long to post. I assume you've already swapped your pump, huh?
Old 07-12-2012, 04:06 PM   #44
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Re: 4.3 Vin X Hard cold start

Quote: Originally Posted by neex
I think you likely have a leak in the pulsator/valve on the fuel pump. I has a similar issue and pulled the thing off and replaced it with fuel line. No start up issues after that. 1 crank and all good. You really should test the fuel pressure at the test valve under the hood to be sure you have a leak.

Good luck and please let us know.
A.
I have a 2001 Crew 4.3 4wdr having the same cranking issues. Doing the key off/on routine solved the problem temporarily But I think the valve you are talking about is failing. Now to my question, where is the valve, inside the tank with the pump or on the outside where I can get at it?

Thank you,

Cidecar2

July 12, 2012
Old 07-12-2012, 05:26 PM   #45
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Re: 4.3 Vin X Hard cold start

Cidecar,

Quite a bit of dust floating around in this thread.

I can't answer as to whether it was the pulsator valve or some other part on the fuel pump, but replacing the pump itself, in the tank, is what solved the problem for me. It's entirely possible that just replacing the backflow valve on the pump (is that what the pulsator/valve is...or is it's purpose similar?) would solve the issue.

Then again, maybe it's just as expensive to replace the entire pump. And if you've got the bed off, or the tank out, you might as well replace the pump while you're at it.

FYI, I've got the LT1 up and running on big injectors, putting about 300hp to the wheels, and this pump is still running great. I've got about 4000 miles on the motor. Plenty of problems to fix, but fuel P isn't one of them!
Old 07-12-2012, 09:59 PM   #46
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Re: 4.3 Vin X Hard cold start

^^^I got 99 problems but a pump ain't one!

I haven't changed the pump on my '02 since it's just a weekend toy and a total PITA to get under it. The pump will be handled when the truck gets torn down for the V8 swap.
Old 07-13-2012, 10:52 AM   #47
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Re: 4.3 Vin X Hard cold start

Definitely worth doing if you've ever got the bed off or the tank dropped, no doubt. Make sure you have extra fuel line fittings--they get VERY brittle after 10+ years.
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