Hi, I'm having trouble with an 87 TBI K5, searched the forum, but didn't come up with an answer. Fuel pump does not work second pump in 6 months, yes it's an Aero-turd, checked all my connections no tears in the wire harness, Brand new pump, strainer, fuel filter. Could this possibly be a problem with the fuel pump relay? Any insight would be greatly appreciated.
CK5
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Fuel pump issue 1987 K5 blazer
- Thread starter Jtownk5
- Start date
There have been people here recently having issues with the fuel hose inside the tank that connects the fuel pump to the pick-up tube (it splits open then you either get no fuel or very little pressure). This hose is special hose called submersible fuel hose. If this is the problem and you try to sue standard fuel hose it will fall apart since it is only designed to have fuel on the inside not the outside.
Even if the fuel pump relay was bad there is a fail safe secondary system to allow the pump to work as long as there is 5 psi of oil pressure. Basically the engine will still start and run as normal BUT it will take a longer crank time before the engine will start since the engine will need to crank long enough to get 5 psi of oil pressure.
Even if the fuel pump relay was bad there is a fail safe secondary system to allow the pump to work as long as there is 5 psi of oil pressure. Basically the engine will still start and run as normal BUT it will take a longer crank time before the engine will start since the engine will need to crank long enough to get 5 psi of oil pressure.
Be sure and check your grounds.
If you can get to the wires, try putting power directly to the pump and see if it will run. But be sure that the ground wire for the tank is good. Otherwise you may think its bad when it isn't.
I helped my mechanic trouble shoot a repeated failure in tank fuel pump problem a year or so ago.
This lady had been to another shop and they had put her in two fuel pumps. They would run about a week and quit.
New pump would seem to fix it.
When my friend got it, we put power to the pump wire, it would not run. We figured maybe just some crappy pumps.
I happened to hook his test light to the tank for a ground, and it would not light when I put power to it.
Checked, and the tank was not grounded.
It had a ground wire, and when we hooked a good ground wire to the tank, the inside lights came on and the key dinger started dinging.
Traced the ground up into the car on the passenger's side, across under the back window where it supplied the ground for the defogger, down the driver's side back door sill, under the driver's side driver door sill, and found a large rusty connection behind the driver side kick panel.
Had about 9 ground wires hooked to it.
After we fixed that, it was like a new car. Power windows worked, inside lights worked, radio would play without cutting off from time to time. And the fuel pump worked.
He charged her about 1/4 of what hours we had in it, since she was older and on a fixed income.
And she bitched. Said we should not charge her for fixing all the other stuff since she had not told us to fix it.
We tried to explain, but she would not hear it. Finally my friend told her there would be not charge, if she would promise to never come back.
Cheap at twice the price.
If you can get to the wires, try putting power directly to the pump and see if it will run. But be sure that the ground wire for the tank is good. Otherwise you may think its bad when it isn't.
I helped my mechanic trouble shoot a repeated failure in tank fuel pump problem a year or so ago.
This lady had been to another shop and they had put her in two fuel pumps. They would run about a week and quit.
New pump would seem to fix it.
When my friend got it, we put power to the pump wire, it would not run. We figured maybe just some crappy pumps.
I happened to hook his test light to the tank for a ground, and it would not light when I put power to it.
Checked, and the tank was not grounded.
It had a ground wire, and when we hooked a good ground wire to the tank, the inside lights came on and the key dinger started dinging.
Traced the ground up into the car on the passenger's side, across under the back window where it supplied the ground for the defogger, down the driver's side back door sill, under the driver's side driver door sill, and found a large rusty connection behind the driver side kick panel.
Had about 9 ground wires hooked to it.
After we fixed that, it was like a new car. Power windows worked, inside lights worked, radio would play without cutting off from time to time. And the fuel pump worked.
He charged her about 1/4 of what hours we had in it, since she was older and on a fixed income.
And she bitched. Said we should not charge her for fixing all the other stuff since she had not told us to fix it.
We tried to explain, but she would not hear it. Finally my friend told her there would be not charge, if she would promise to never come back.
Cheap at twice the price.
zombie1969
1/2 ton status
No good dead goes unpunished.I've tried a couple things so far and no go, gonna have to wait till daylight to work on it again. I checked the wires going to the fuel pump at the frame connector and I'm not getting power to the pump. I do have spark and it will fire and run if I squirt fuel into the intake, I found a post on here that says it could be a bad ign module, I hope not. It will be another 2 weeks till I have it running again.
If you can put fuel down the TBI and it will run then it IS NOT a bad ignition module. Remember that you will ONLY get power to the frame connector for 2 seconds unless the engine is running. Hook your meter up to the wires THEN have a friend turn the ignition switch to the run position while you check for voltage, if there is voltage it should go away after about 2 seconds.
The other thing you can do is put 12 volts to the single red wire hanging off the fuel pump relay and this will force the pump to run (assuming it isn't a bad pump or wiring in between).
The ignition module on engines with distributors controls the firing of the injectors as well as the spark,and its very possible only the "fuel" portion of the module is crapping out intermittently..
We had a 90's Oldsmobile with the ground wire dilema at my friends shop..he installed 2 "good used" fuel pumps and a third brand new one,and all three died shortly after installing them..after new pump #4 went in,we talked to a real good tech who worked at dealerships and junkyards,and he suggested we check the ground wires under the passenger side kick panel..we did,and they were all gangrene,and the car itself was so rotted where they were screwed to the metal there was no way they were getting a good ground..as soon as we hooked a jumper wire to a better ground,the pump started working,and sounded faster than any of the previous ones too...car ever came back again,after weeks of frustration,and battles with its owner!..
Sadly,the guy who diagnosed the problem,died only a few weeks later,at age 50--heart failure..
I've seen a defective oil pressure switch pevent a fuel pumpfrom working,or letting it die after working a few minutes..
We had a 90's Oldsmobile with the ground wire dilema at my friends shop..he installed 2 "good used" fuel pumps and a third brand new one,and all three died shortly after installing them..after new pump #4 went in,we talked to a real good tech who worked at dealerships and junkyards,and he suggested we check the ground wires under the passenger side kick panel..we did,and they were all gangrene,and the car itself was so rotted where they were screwed to the metal there was no way they were getting a good ground..as soon as we hooked a jumper wire to a better ground,the pump started working,and sounded faster than any of the previous ones too...car ever came back again,after weeks of frustration,and battles with its owner!..
Sadly,the guy who diagnosed the problem,died only a few weeks later,at age 50--heart failure..
I've seen a defective oil pressure switch pevent a fuel pumpfrom working,or letting it die after working a few minutes..
The ignition module on engines with distributors controls the firing of the injectors as well as the spark,and its very possible only the "fuel" portion of the module is crapping out intermittently..
We had a 90's Oldsmobile with the ground wire dilema at my friends shop..he installed 2 "good used" fuel pumps and a third brand new one,and all three died shortly after installing them..after new pump #4 went in,we talked to a real good tech who worked at dealerships and junkyards,and he suggested we check the ground wires under the passenger side kick panel..we did,and they were all gangrene,and the car itself was so rotted where they were screwed to the metal there was no way they were getting a good ground..as soon as we hooked a jumper wire to a better ground,the pump started working,and sounded faster than any of the previous ones too...car ever came back again,after weeks of frustration,and battles with its owner!..
Sadly,the guy who diagnosed the problem,died only a few weeks later,at age 50--heart failure..
I've seen a defective oil pressure switch pevent a fuel pumpfrom working,or letting it die after working a few minutes..
The ignition module has nothing to do with the fuel pump getting power to it so you can rule out a bad module.
There is no way a bad oil pressure switch would stop the fuel pump from working UNLESS the fuel pump relay is bad. The oil pressure switch is a backup fail safe in case the fuel pump relay does go bad it will allow the pump to continue working.
It lives
I rechecked the wiring to the fuel pump, power wire for the fuel pump was broken off inside plug for the sending unit/fuel pump on the frame rail, pulled it apart and soldered the wire to the pin and put it back together. Turned on the key cranked over twice and fired up, runs like a champ. Thanks for your insight
I rechecked the wiring to the fuel pump, power wire for the fuel pump was broken off inside plug for the sending unit/fuel pump on the frame rail, pulled it apart and soldered the wire to the pin and put it back together. Turned on the key cranked over twice and fired up, runs like a champ. Thanks for your insight
Alan2smiley
I'm in the shop
Does this look familiar?
