Fuel pump relay intermittently working

[E30SPDFRK]

This started a few weeks ago. I was driving home from school when the car stalled slowing for a stop sign. I thought I had maybe just stalled it without knowing, but it happened a few more times before I got home. Each time it happened, the car would crank for around 15 seconds before starting. I left it running in my driveway for about 10 minutes and it seemed fine, so I shut it off. But later that night I went to start the car and it wouldn't start at all. I found that the fuel pump relay wasn't clicking on, so I swapped it with a new one to no avail. I left it for a day and it started right up and worked fine. It has been randomly working since.

The e34 harness grommet doesn't fit through the firewall, so I was thinking that maybe the metal had chewed through the insulation on the wires and it was intermittently shorting out. The car was running while I was checking this, but stalled randomly and wouldn't start again. I was dropping the glove box straps and wasn't even near the wires. They all looked to be good as well, but I threw some electrical tape around them individually to be sure.

The confusing part is that when the car stalls, it dies quickly; not a slowly running out of fuel stall. The main relay clicks normally.


Any ideas?

[Spinning Tires]

I had the same exact problem with my stock 87 is. That is if you dont get spark also. Theres 2 wires coming from the battery in the trunk. the skinnier one powers the ecm, fuel pump and ignition. The tricky part was that even when the car didnt start, the wire would still feed enough power to light up my test light. The wire was slightly corroded at the battery. I took the easy way out and just attached the small wire at the junction block under the hood to the fatter wire. problem solved

[E30SPDFRK]

All my wires are securely fastened and corrosion free. I have 12v at the 30 socket for the fuel pump relay when the key is turned on, but it goes to around 9v when I click the key to start. Is that normal?

I tried heating and cooling the ecu just to be sure it wasn't a temperature issue but there was no difference.

[Spinning Tires]

just switch that wire over and see what happens. it only takes 1 min. you take the nut off at the junction block on the passenger side firewall. remove the wire going to the fuse block and switch it over to the nut on the battery terminal end right about it. it took me a week to figure this out. like it said you still get power coming from it which made it tricky to find. i'll post a pic if you need one

[E30SPDFRK]

I would like a pic if you don't mind as I'm not sure what you're talking about.


I tried another ecu today and it was no different.

[E30SPDFRK]

Is there a way to test the CPS to see if its working?

[Spinning Tires]

OK so heres the pic. bear with me because i dont even have a motor in the car so i dont have any wires hooked up.




you take the wire off the nut circled in green that is traveling in the direction of the green arrow to the fuse box. And you attach it to the terminal circled in red. even if its just temporary like with vice grips or something just to see if that fixes the problem. Hopefully it does cause i had to dig through 2 feet of snow to get my hood open.
also it doesnt seem like a cps because that doesnt control your fuel pump. just ignition and fuel

[E30SPDFRK]

Haha, I had to dig the car out too.

So you're saying to just put power directly to those wires rather than letting it go through the junction box? Would this mean the junction box is going bad?



I was thinking the cps because mine looks pretty ratty and because of the way the car stalls. If it stops telling the ecu that the engine is spinning, the ecu would cut spark and power to the fuel pump relay.

[Spinning Tires]

no it measn that the skinny wire going to the junction block is back. apparently according to alldata, the smaller wire has a fuseable link. all i know is i hooked the skinnier wire going to the fuse box, up to the fat wire coming from the battery. i never had the problem again. To be honest, the problem your having cpuld be a large number of things but i figured what i gave you was a hard problem to diagnose but an easy problem to test

[E30SPDFRK]

CPS fixed it