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Old 06-18-2019, 12:49 AM   #1
hondo78
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1989 crew with TBI/electrical/fuel delivery issue

I drove my new to me, 4 door '89 home a couple of weeks ago. On the way, the "Check engine light came on and then the power cut off"; Next CE light off and it roars to life; Again "Power off and light on" repeat, repeat, repeat. So I replaced, cap, rotor, wires and the ICM in the TBI distributor.

Next: I replaced the fuel filter as a test, and just received the new fuel pump this evening. (I am convinced this is electrical in nature)

Someone mentioned there is a relationship with the fuel pump power supply and oil pressure so tonight I did some online reading; ChevyTech had helped someone in 2006, with a very similar issue, that turned out to be the fuel pump relay, and possibly the ECM as the garage in the story replaced that too. "This was under 91 oil pressure switch bypass"

This is very close to my issues; however mine has not failed to start, 'matter of fact it idles well, but under acceleration it shuts off, possibly the oil pressure dropping turning off the fuel pump or the sending unit is failing?

Anyone have the same issue at some point?
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Old 06-18-2019, 08:12 AM   #2
Katrina/10
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Re: 1989 crew with TBI/electrical/fuel delivery issue

The oil pressure switch is just a backup for the relay. As long as the distributor is spinning, the ECM will energize the relay. There is also a fuel pump test wire on the relay connector. It's a loose wire with a plug on it, can be connected to 12V to run the fuel pump directly. You should hear the pump running with the engine off.
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Old 06-23-2019, 12:15 AM   #3
hondo78
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Re: 1989 crew with TBI/electrical/fuel delivery issue

Quote:
Originally Posted by Katrina/10 View Post
The oil pressure switch is just a backup for the relay. As long as the distributor is spinning, the ECM will energize the relay. There is also a fuel pump test wire on the relay connector. It's a loose wire with a plug on it, can be connected to 12V to run the fuel pump directly. You should hear the pump running with the engine off.
The problem is itermitint, if the little coil under the ICM was failing or grounding, that might cut the signal to power the fuel pump, wouldn't it?
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Old 06-23-2019, 07:21 AM   #4
Katrina/10
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Re: 1989 crew with TBI/electrical/fuel delivery issue

Yes, it would. Did you replace the pump?
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Old 06-23-2019, 12:31 PM   #5
diveplane
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Re: 1989 crew with TBI/electrical/fuel delivery issue

Quote:
Originally Posted by hondo78 View Post
I drove my new to me, 4 door '89 home a couple of weeks ago. On the way, the "Check engine light came on and then the power cut off"; Next CE light off and it roars to life; Again "Power off and light on" repeat, repeat, repeat. So I replaced, cap, rotor, wires and the ICM in the TBI distributor.

Next: I replaced the fuel filter as a test, and just received the new fuel pump this evening. (I am convinced this is electrical in nature)

Someone mentioned there is a relationship with the fuel pump power supply and oil pressure so tonight I did some online reading; ChevyTech had helped someone in 2006, with a very similar issue, that turned out to be the fuel pump relay, and possibly the ECM as the garage in the story replaced that too. "This was under 91 oil pressure switch bypass"

This is very close to my issues; however mine has not failed to start, 'matter of fact it idles well, but under acceleration it shuts off, possibly the oil pressure dropping turning off the fuel pump or the sending unit is failing?

Anyone have the same issue at some point?
first thing to check is battery terminals and corrosion on them i replaced mine with new pegs every few months i check them.
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Old 06-23-2019, 02:09 PM   #6
hondo78
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Re: 1989 crew with TBI/electrical/fuel delivery issue

No on replacement of the pump, I received one that was damaged, new unit has shipped, also this morning was very quite, I can't hear the fuel pump running. I have "no place here" to rebuild the distributor. So I have a complete new China distributor coming, I'll rebuild the old one once I'm back in AZ.
I have not found an issue with grounds or power connections.
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Old 06-24-2019, 05:27 PM   #7
sntrym95
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Re: 1989 crew with TBI/electrical/fuel delivery issue

It does sound like something in the distributor. Almost like in an old dizzy, if the advance wasn't set right, the engine would die on acceleration.

Not that you can control the advance anymore, but if you have a multimeter you can check resistance at various points like the ignition coil. There are various articles on here that describe some of the things you can check.
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