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fuel pump relay ????


my70chevelless
11-20-2007, 03:13 AM
I have a 1987 S10 blazer with the 2.8L v6. I was driving home last night when all of the sudden she just quite as if the key was turned off. I waited about 10 min. & she fired back up & went about a few miles & did it again. After another 10 min. she started & I got her home.
I listened for the fuel pump & heard nothing waited a while tried starting her & she fired up ran for about 15 min then quite. I checked the relay for volts she had just over 11 volts. I then took the relay off and jumped the orange & tan wires & the fuel pump turned on.
I tried the relay next to her as they are the same & nothing. I put that relay back & jumped it again & the pump worked.
My question is could this be a bad relay? Since I'm not sure what the other relay does I don't understand why this would have not worked unless it too is bad. I also heard something about an oil pressure switch or relay that also runs the pump is this true & if so where is this located as my oil pressure jumps around from 40-near 0 but has been doing this ever since I have had her & she has always ran fine. Any help would be appreciated as this is my only ride for the winter. Thank you!

MT-2500
11-20-2007, 08:49 AM
If you can jump orange and tan/white and fuel pump runs.

The fuel pump and power to it is OK.
Orange is power feed.

Is the computer turning on relay?
Does it trip on with engine cranking or running?

The oil pressure feeds power to fuel pump when engine is running or you have oil pressure.
It is only there to run fuel pump if relay fails and only works when engine is running.
Will it start and run when fuel pump is jumped?
Are you losing any spark when it quiets?

my70chevelless
11-21-2007, 11:20 PM
I replaced the relay tonight & she fired right up & ran a good half hour or more. So I figured I would shut her down & then start her back up nothing no fuel pump noise but a click in the relay. So I waited 15min & she fired right up & ran for about 10min. died. I called a friend who is a mechanic & he said that he thought it was the ignition module. And next time it dies check spark which I did & there was a good spark. I called him back to let him know & he still said it was the module!. This I can't figure out as I always thought that I would not have a spark. Anyway as I was talking with him I re started her & she ran a good hour until I shut her down then tried to re start her but nothing. So now I'm really confused as to why he insists its the module?
Another thing I noticed it seems as though when the pump primes I can tell when she is going to start or not as it's louder when she is going to fire up weaker sound when she is going to give me trouble & of course no sound when she doesn't want to start. At least I hear a good click from the new relay but can not figure out why my friend thinks it the module & said that if it were the pump it would just die?. Now I'm really confused & why she seemed as if for at least 3 times tonight she would of ran all night if I had not shut her down? but not re start right away!.

my70chevelless
11-21-2007, 11:25 PM
If you can jump orange and tan/white and fuel pump runs.

The fuel pump and power to it is OK.
Orange is power feed.

Is the computer turning on relay?
Does it trip on with engine cranking or running?

The oil pressure feeds power to fuel pump when engine is running or you have oil pressure.
It is only there to run fuel pump if relay fails and only works when engine is running.
Will it start and run when fuel pump is jumped?
Are you losing any spark when it quiets?
Thank you for your help!. Yes the computer is turning the relay on as I here a click in the relay. It trips on when cranking!

MT-2500
11-22-2007, 09:08 AM
Thank you for your help!. Yes the computer is turning the relay on as I here a click in the relay. It trips on when cranking!

Is the relay putting good voltage to the fuel pump?
Our of relay and all of the way back to fuel pump?
Can you jumper the fuel pump and get it to run?
How much fuel pressure is the fuel pump putting out when it is rinning?

DelCoch
11-24-2007, 03:05 AM
Check the battery with a load type tester. AutoZone, etc, will do it for free. A weak battery will cause the problem you're having, as the starter will draw all the current away from the fuel pump with a weak battery.

Next, when you have the no-start I would check the fuel pump pressure with a fuel pressure gauge. It takes more fuel pressure to start the engine than it does to keep an engine running.

Post back your findings and we can help you further.

error_505
11-24-2007, 11:38 AM
My 98 was doing almost the same thing. I had great fuel pressure but did not hear the pump.......i replaced relays and such as you tried........ended up being the ignition module though. I found out after buying relays, coil and something else.......lol mine runs good now an starts every time *knocks on wood*

my70chevelless
11-26-2007, 05:43 PM
A friend of mine who is a mechanic said the same thing too me that it was the ignition coil!.
The only problem I have with this is that the last time she died I still had good spark at the plug wires. I would think that if the ignition coil was bad I would have no spark am I wrong?
When this problem happened too you did you have good spark or no spark?. Thank you!

bozr
11-26-2007, 07:12 PM
Fuel pumps can die like that too.
They run for 10 to 20min. then the motor locks up, after they cool down you can repeat the process over again.

Check the fuel pump test connector for voltage to ground when the fuel pump should be running (key on prime). If it's the fuel pump you will have 12v at the connector but the pump will not be running.

You can rule out ignition by spraying carb cleaner directly onto the throttle while starting.

error_505
11-26-2007, 11:46 PM
Mine was the Ignition Module. It is the little module on a bracket in front of the coil. I replaced the coil 1st. Yes I did show spark most of the time as well. I pulled a pressure test on my pump and it was 100%

Good Luck

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