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Mafia_Insurance

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Discussion starter · #1 ·
1987 blazer 2.5 4 speed manual

Car won't start.
Car has gas
car has sufficient battery power
All fuses normal
Relays are functional
Motor has spark (runs with gas on the TB)

Now the interesting part.
Fuel pump doesn't work (doesnt prime)
Headlights dont work. (?)
Interior lights dont work. (?)

Everything else electrical, including electric fan, works. What is going on. I suspect a ground, but i checked all grounds and they all seem ok; i must find where does the connection between the non-functioning items is so i can work on it. Help. The car is on a Downtown Miami parking lot, and may get towed soon. :( Any suggestions appreciated, im working against the clock.
 
#2 · (Edited)
Good grief!!

We gotta get you out of the parking lot.

Run a 14 gauge wire from the positive battery post to the hot side (electrical feed) of the fuel pump and get the pump to run. You have a definite electrical issue, probably forward of the tank, but no time to trouble shoot it. You may be able to "hot up" the pump at the fuse panel or at the fuel pump test wire, hanging loose at the firewall...wiring it direct should get you going....ya gotta get the otherwise good fuel pump to run.

If it is a ground issue AT THE PUMP, you must fix that first, it is one of the wires off the top of the tank, IIRC.
 
Discussion starter · #3 ·
The adapter that is in the back of the car, behind the gas tank, which holds a ground to the beam, and the cable that powers the license plate lights; in that adapter, the other wire is the live one for the pump ? Im gonna get the wire from the license plate light and plug it to the fuel pump feed wire, also, im gonna disconnect the ground nearby and sand it down to the metal, to make sure that isn't it either; that should get it running yeah ?
 
#4 ·
Mafia_Insurance said:
The adapter that is in the back of the car, behind the gas tank, which holds a ground to the beam, and the cable that powers the license plate lights; in that adapter, the other wire is the live one for the pump ? Im gonna get the wire from the license plate light and plug it to the fuel pump feed wire, also, im gonna disconnect the ground nearby and sand it down to the metal, to make sure that isn't it either; that should get it running yeah ?
Click to expand...
================
M.I.---

You are in desperate need of one of these:

http://www.bosstoolsusa.com/index.asp?PageAction=VIEWPROD&ProdID=3765

You can use this to find out if you have 12v at the pump. Fix the ground there first. It may be all you need to do to get the pump to run..good luck. The brainbox will hot up the pump for but a few seconds to pressurize the fuel rail and then the power in the feed wire "goes away" and is brought back on by the fuel pump relay AFTER it sees 4 pounds of oil pressure. If the engine will run by adding gas to the throttle body, you can figure that the relay is good. If you power the pump with the license plate light power feed wire, the pump should run when the park lights are on.
 
#6 ·
Mafia_Insurance said:
k, so i just need to hook it up and go ?
Click to expand...
==================
M.I.---

If the pump somehow died on you, nothing but a brand new AC Delco fuel pump is going to get it going. If the existing pump will run--wired into the tail lights--it'll start and get out of that parking lot/tow-away zone. And, if the pump IS dead, your cheapest way out of this fix is a tow..the cost of bailing out your rig from an impound yard is high dollar...

If you splice or "T" into the pump feed harness wire, remember that you will then be powering up a harness wire that was previously "dead" forward of the tank. What this will do, or bring on, I don't know. You are backfeeding the forward circuits. Would be best to power the pump direct.
 
Discussion starter · #7 ·
im gonna run 2 wires,
will it be better to:

-connect one wire from the negative battery post to the pump ground
-connect the other wire from positive post of battery into pump feed

or

-connect ground to chassis ground
-connect pump feed to positive battery terminal

thanks !
 
#8 ·
Mafia_Insurance said:
im gonna run 2 wires,
will it be better to:

-connect one wire from the negative battery post to the pump ground
-connect the other wire from positive post of battery into pump feed

or

-connect ground to chassis ground
-connect pump feed to positive battery terminal

thanks !
Click to expand...
Either way you decide on, include an in-line fuse.
 
#9 ·
Dont do the light circuit power feed, do the fused wire from the battery feed. The extra current draw on the light circuit could damage the light switch, the wiring or blow the fuse for the lights.
 
#11 ·
You just need the pump and strainer and fuel filter, the pump is $80 at orilleys (AC DELCO).
 
Discussion starter · #12 ·
well the mechanic couldn't find the problem and he made a bypass to the fuel pump to run it, and it ran great. However, as we were testing it, i found the real problem : A fusible link was loose, the one that attaches to the back of the alternator and feeds the relay. Once i tightened it everything worked fine, but i still kept the bypass just in case; he did it with the inline fuse, so i just took the fuse out, im keeping it in the glovebox just in case. Thanks guys.
 
Discussion starter · #13 ·
It idles high sometimes now.

Sometimes it idles normal, sometimes it idles high, and comes back down slowly (sounds like EGR or vaccum)
In the morning it turns on great but it struggles a bit in low rpm's and gets back to normal (for a little bit) when it reaches 160*, but then after a short run, it idles high again.
My PCV valve hose is loose, which i will address also.
Suggestions?
 
#14 · (Edited)
Mafia_Insurance said:
It idles high sometimes now.

Sometimes it idles normal, sometimes it idles high, and comes back down slowly (sounds like EGR or vaccum)
In the morning it turns on great but it struggles a bit in low rpm's and gets back to normal (for a little bit) when it reaches 160*, but then after a short run, it idles high again.
My PCV valve hose is loose, which i will address also.
Suggestions?
Click to expand...
=====================
M.I.--

I've got my Duke's goofy idle narrowed down to a non-OE EGR valve. It drives me nuts...

Almost all high idle complaints can be traced to a vacuum leak somewhere.

For sure, you need to fix the PCV leak. When I look at the OE PCV System, the whole thing looks just like a massive vacuum leak. There's vacuum right to the PCV valve and the "other" side of it is a fresh air intake (vacuum leak) through a large hose at the rear of the valve cover, going to a "horse-hair" filter mounted inside the air cleaner. ANY vacuum leak or partially stuck/worn out PCV valve will throw the idle stability off.

The ignition timing will jump around, too. Any vacuum leak will make the timing jump around, adding to the "funny" idle. This you can "see" with a timing light and simply watch the timing "move" as the idle jumps around. Also, the intake air temperature sensor, if it is coated with black shyte, from the EGR valve working normally or abnormally, will cause the timing to move, affecting the idle speed. If you ground out the ALDL, like when you do this to set "base timing" then the advance and retard of the timing jump ceases. And the idle often smooths out.

All this tells me that the timing advance/retard built into the
ignition module and brainbox is REALLY sensitive, far more so than I originally thought.

The timing advance/retard is based on measured temperature. Coolant Temperature and Intake Air Temperature. Those two sensors are almost certainly running the whole "timing" show. I do not know what parameters or "trigger points" are built into the OBD1 system, but I do know that these two points on a later, OBD2 system are 86* F. (for intake air temp) and 212* F. (for coolant temp). As the system gets close to these two points, the timing begins to retard, costing both performance AND fuel economy.
 
Discussion starter · #15 ·
Steady Eddie said:
=====================
M.I.--

I've got my Duke's goofy idle narrowed down to a non-OE EGR valve. It drives me nuts...

Almost all high idle complaints can be traced to a vacuum leak somewhere.

For sure, you need to fix the PCV leak. When I look at the OE PCV System, the whole thing looks just like a massive vacuum leak. There's vacuum right to the PCV valve and the "other" side of it is a fresh air intake (vacuum leak) through a large hose at the rear of the valve cover, going to a "horse-hair" filter mounted inside the air cleaner. ANY vacuum leak or partially stuck/worn out PCV valve will throw the idle stability off.

The ignition timing will jump around, too. Any vacuum leak will make the timing jump around, adding to the "funny" idle. This you can "see" with a timing light and simply watch the timing "move" as the idle jumps around. Also, the intake air temperature sensor, if it is coated with black shyte, from the EGR valve working normally or abnormally, will cause the timing to move, affecting the idle speed. If you ground out the ALDL, like when you do this to set "base timing" then the advance and retard of the timing jump ceases. And the idle often smooths out.

All this tells me that the timing advance/retard built into the
ignition module and brainbox is REALLY sensitive, far more so than I originally thought.

The timing advance/retard is based on measured temperature. Coolant Temperature and Intake Air Temperature. Those two sensors are almost certainly running the whole "timing" show. I do not know what parameters or "trigger points" are built into the OBD1 system, but I do know that these two points on a later, OBD2 system are 86* F. (for intake air temp) and 212* F. (for coolant temp). As the system gets close to these two points, the timing begins to retard, costing both performance AND fuel economy.
Click to expand...
damn dude :worship:
 
#16 ·
LOL---

M.I., now you know why I am anal about the 180* t-stat mod AND making sure that no underhood hot air gets into the intake (the low buck CAI mod). The whole point is the avoidance of timing retard. All these mods are unseen and designed to take advantage of what the Pontiac Powertrain Engineers gave us. We do not have much horsepower to begin with, and to lose some of it to easily avoided timing retard, is,
(pun intended) retarded...:D
 
#18 ·
Mafia_Insurance said:
im sorry, whats the 180* tstat mod ? i have a 160* t-stat on right now
Click to expand...
====================
The 180* t-stat is listed as an "alternative" temperature range t-stat by AC Delco as being a cooler one OK for use. The 160* t-stat I avoided because I thought it a bit too cold, and *might* trigger an SES light and set a code. If it works for you, I see no reason to change it out. Carbon in the intake tract is the problem here. A cooler running Duke is a good thing, too cool may add black junk to the insides of the intake.

The uses for a 160* t-stat are primarily for drag race uses, and to use one in a late model OBD2 set-up requires a tuning change, but like I said, if it works for you, keep it.
 
#19 ·
HEY that exact thing happened to me i was driving to work and everything just quit working the prk brk light was on and the check engine light was on no lights worked or anything it would crank but no gas i had it at work for a couple of days working on it till a mechanic friend looked at it and found the problem the fusable link going to the alternator, that was it still works fine
 
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