MSD 2225 Installed, Now Fuel Pressure Drops

[new2trucks]

I have an 01 S10 with a stock 4.3 stock as my daily driver. I've had many issues with it and I've been able to read old threads for help on the majority of the issues. For a back ground, I've done a tune up (plugs, wires, cap, rotor, fuel filter), new egr valve, sea foamed, coolant temp sensor and CPI upgrade in the past year. I've gone through 3 fuel pumps in the last year, and when the last one went out on me last week, I decided to go with the MSD 2225 that people have done on this board and I also changed the fuel filter again. I followed the instructions that were posted on this board.

The truck runs now, but not well. I have a low fuel pressure problem starting as early as 2-2,500 rpms under a load. I hooked up a gauge to it and off the pressure is @ 60, started and idling is around 54-56 (but a little spikey), and reving it it park it tends to get a little more spikey but stays between 52 and 58.

The problem occurs when I'm driving. If under load or anything past 1/3-1/2 throttle and above 2,500 rpms, the psi drops down to 30 and fluctuates A LOT! It causes the truck to bog, but has yet to die on me. As long as I baby it, it runs fine, but it doesn't help in lane changes or freeway merges.

My question is, could this be a problem with the pump itself (like i got a bad one), or could it be a power issue? To ground the pump, I used the ground strap that goes from the filler neck to the frame. Could it be drawing too many amps under load and giving out? Or is there some other reason that the fuel pressure drops under this type of load? Any help would be appreciated!

[Solid10]

I am not a professional but i want to help as best i can.
My truck would crank fine, run great if i babied it, but under any load i mean...before the throttle would even think about downshifting it would bog and spitter and sputter and damn near die but didn't.
It felt like the transmission-sometimes timing, fuel pump, FPR-then i found out it was something small n simple.
fuel filter.
this might not help at all but i tried! keep us posted

[new2trucks]

Thanks for the thought Solid10. When I changed the fuel pump, I didn't have time (nor energy due to the 100+ degree weather) to change the filter, so that was my first hope/guess. I changed the filter 2 days ago and it didn't change a darn thing.

Does anyone know of a way to check the amps the pump is pulling/getting when the truck is running? I don't know if that could be it since it's not like the pump needs to pump more at higher revs. It just seems to act up when the engine is under a load, and it creates the fuel pressure to drop=no power.

[Solid10]

hm i will talk to the other mechanics up here since most of them used to work at car dealerships!

I'm only 18 and have worked here a year so i haven't experienced many problems with fuel pumps and such.
I will let you know tho

[new2trucks]

Ok...I just got off the phone with MSD, and I think I goofed. I mounted the pump on the frame rail right next to the tank. The rep told me that the pump is a pusher not a puller, so there needs to be a constant flow to the pump in order for it to work. Since the feed is coming from the top of the tank, the rep said that it's probably not getting enough fuel from the tank in order to pump it to the engine bay.

Any of you guys with the MSD 2225 have this issue? (Not the people using this pump as an assist, but who have removed the stock pump and are only using the MSD 2225).

Also, where did you mount yours?

[dragginesva]

just finished working on mine last night... i used the 2225 and mounted it on the frame rail before the filter under the cab... i have a bottom feed cell so gravity sends fuel into my pump all the time... i think the msd rep is right because the pump will strain trying to pull the fuel up and out of the tank and pump high psi at the same time... only other time i have heard of this problem is if the return line back to the tank is restricted

[new2trucks]

Thanks for the info dragginesva...wish I wouldn't have rushed into this one as fast as i did. I think I'm gonna look into the walbro in tank pump now...probably get rid of the 2225, unless anyone knows how to turn a stock tank into a bottom feed without welding.

I'm getting real tired of pullin the damn bed off...

[new2trucks]

Hey everyone...just wanted to give an update to anyone who cares...
I don't want to run an internal pump on this thing, so I called SUMMIT to see if they can advise of a pump that would work, and they said that the MSD should be able to pull the fuel out as long as it is in within 1 food of the tank. They said that I may have a faulty pump.

I started thinking about it, and I did not replace the plastic tubing in the housing of the stock fuel pump with rubber hose. Does anyone think that the suction of the MSD could be collapsing the plastic accordian style tubing that is there?

By the way...the problem has gotten a little worse as i get a pressure drop in park/neutral as well now. As long as I baby the truck, it gets around.

[Yogi]

Quote: Originally Posted by new2trucks

Hey everyone...just wanted to give an update to anyone who cares...
I don't want to run an internal pump on this thing, so I called SUMMIT to see if they can advise of a pump that would work, and they said that the MSD should be able to pull the fuel out as long as it is in within 1 food of the tank. They said that I may have a faulty pump.

I started thinking about it, and I did not replace the plastic tubing in the housing of the stock fuel pump with rubber hose. Does anyone think that the suction of the MSD could be collapsing the plastic accordian style tubing that is there?

By the way...the problem has gotten a little worse as i get a pressure drop in park/neutral as well now. As long as I baby the truck, it gets around.

I would suspect the accordion tubing. It's made for pressure not vacuum.

Is the MSD pump below the bottom of the tank? If it is, the MSD pump should work from the top or from the bottom. Once you have established flow from the top, the siphoning effect fills the suction of the pump, and it is the same as if it were pulling off the bottom. The "suction head" in engineering terms is the same with the line coming over the top or out the bottom.

[MikeInCtown]

+1 on tubing check. The lines are made for pressure not vacuum.

[new2trucks]

Thanks you two. Looks like the bed has to come off again...damnit

Yogi-The pump isn't underneath the tank. I have a 4/5 drop on it, and trying to mount it anywhere below the tank would have it below the frame and then scrapped off... It's mounted on the frame rail right next to the tank. I would say it's about dead center on the tank, but I did try to put as low as possible.

Because of that, do you think I'll have a problem with the siphoning effect after I get to about half tank? The pics I've seen on this forum of mounting have been above the tank...with the exception of some with fuel cells.

I really appreciate the help on here. This forum has been a life saver for me and this dime, not to mention a money saver.

[Yogi]

I can see that the pump might have a problem sucking when the level in the tank drops below the level of the pump. However, the fact that you have seen pics of the pump mounted above the tank shows that others have made it work by sucking from the tank. Sometimes it works and sometimes it will have problems. You're asking the pump to do something that it is not designed to do.

[MikeInCtown]

IIRC the fuel tank is mounted level with the rail at the bottom. I would lower the pump if possible and if need be make a bracket for it to get it level with the tank bottom. Doesn't really need to be below the tank, just at the bottom.

[new2trucks]

Hey All...just wanted to close out this thread with what I did, and so far the truck is running great again! It's only been 2 days, and I have over half a tank still, so I'm keepin my fingers crossed as the tank empties.

Here's what I did:
I pulled apart the pump housing again, and replaced the plastic tubing with some efi fuel line. I also replaced the filters in the tank (something I didn't do originally, just kept the old). The plastic tube was very spongy in 1 area and seemed to be cracked too.

I didn't move the pump location, but only because I don't have a tap'n'dye set at home, and to mount it on the bottom of the frame rail where the tank and frame are about level, I could not get between the two to access the bolt...so I figured I give it a try as isfor now.

So far so good, but like I said, I'm still over half a tank. Also, I could tell that I was definitely putting a load on the pump that it didn't like as it is now MUCH quieter...I just hope that I didn't take too much life out of it driving like that for so long...

[Bill Wheats]

Good job. We learn something every day.

[Yogi]

The tubing that you replaced, was it the accordion tubing in the tank?

Congrats!

[new2trucks]

Quote: Originally Posted by Yogi

The tubing that you replaced, was it the accordion tubing in the tank?

Congrats!

Yup, that's the one I replaced. I'm at a little under a half a tank today (drove a lot yesterday...), and so far so good! Thanks a lot to all those that helped me out on this one!

[What?]

drats, little late for me to reply, I cut and remove completely of accordion line and replaced with hose straight to bottom of tank but with a gap of room, pulled stock pump out, I mount the pump near level top of fuel tank and no problem