Buick gremlin strikes again

[Mmffnick]

hey guys here's what's going on after the new engine install finally I'm slower than a 7 year itch lol the cars fuel pump will not prime its self on the initial start up if u manualy prime pump it will start every time after that till it sits and the fuel pressure drops beyond the point to start the car heres what I have checked oil pressure switch grounds relays it has a new sender in the tank new pump Hotwire kit is there something I'm not seeing or checking any ideas would be helpful tks

 

[TurboBuRick]

Sound like the ecm might have lost the fuel pump signal. The ecm sends ground to the relay coil.

You can jump the relay plug with a small jumper wire. Jump B and D. The pump should then run with the key on.

 

[Mmffnick]

I'll try it this morn thanks

 

[RmvBfrFlght]

Sound like the ecm might have lost the fuel pump signal. The ecm sends ground to the relay coil.

It is actually the opposite, the ECM sends +12 volts to the fuel pump relay coil to activate it. This is true for the '84-'85 and the '86 -'87 ECMs. There is a small transistor that likes to fail, easy to replace it with a PN2907.

I have a post here someplace that shows which one it is in the '86/'87 '7148 ECM. It is likely very similar to the '84/'85 ECM.

Of course the relay just may be bad.

RemoveBeforeFlight

 

[TurboBuRick]

Ugh... Thanks for correcting me Bob. I had to go out to the garage to confirm. I was wrong.

 

[Mmffnick]

I found the problem today had to pull the finder and inner fender to find that several wires had came in to so it has been a long day of putting it back together don't really know how the car was running at all guess it's just tired of sitting lol

 

[RmvBfrFlght]

Ugh... Thanks for correcting me Bob. I had to go out to the garage to confirm. I was wrong.

With the ECM providing a ground for everything else but the IAC it is an easy mistake. And easy to pop that transistor while troubleshooting. On newer ECMs that used that same transistor setup they went to a heavier duty one. Now while troubleshooting the slightest short doesn't just take out the transistor, it fries the board trace, ack.

RemoveBeforeFlight

 

[RmvBfrFlght]

I found the problem today had to pull the finder and inner fender to find that several wires had came in to so it has been a long day of putting it back together don't really know how the car was running at all guess it's just tired of sitting lol

How I know, with cars this old there is always something to work on. Good job on finding the issue.

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[Mmffnick]

When I use the jumper wire it activates the fp but still won't with the relay u think it might have burnt out that transistor then

 

[Mmffnick]

Also I have tried a new relay already

 

[RmvBfrFlght]

In this case it is likely the ECM (that little transistor). At the ECM pin A1 (DK GRN/WHT) is the relay drive signal (12 V). It goes to relay terminal A, with terminal C being ground. Can measure the voltage at A to another ground, and if good check that terminal C is grounded.

At key-on, engine-off the ECM will activate the relay for 2 seconds. Should be able to measure +12V during that time. Need to key-off for 10 seconds before keying-on again.

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