Hi all,
First time post so I hope this is the right spot.
I have an 87 L98 C4 and up to about 2 months back it used to cold start fairly well.
Then I found if it was a cold start (6 hours or more) I would have to run the starter for up to 30 seconds for it to start. It went well when going.
I looked for similar posts and didn't quite find the same symptoms however many people just replace pumps, regulator or relay.
There were comprehensive articles on fuel diagnostics but not quite the description I was looking for.
So I studied the circuit for a bit.
The relay energizes for about 2 seconds on initial turn on from cold just to pre-charge the fuel system.
It then energizes while the starter is engaged. That's it. It isn't used while the motor is running.
The Oil pressure switch takes over powering the fuel pump.
As my engine ran well when started I assumed I didn't have a pump, regulator or Oil pressure switch issue.
The 20-30 second grind on the starter could easily be explained if it was waiting for oil pressure to come up before it got fuel.
I was also confident that timing, injectors, fuel filter and 9th injector were all good as I'd given the car a comprehensive tune up 6 months earlier.
Sure enough the relay was the issue.
It wasn't toast as I pulled it apart and checked for burn contacts and tested its operation.
Poor contacts on the relay pins and its connector was the only issue.
This connector is 31 years old so I suppose that sort of thing is expected.
Anyway some contact cleaner and a quick polish on the connector and pins and its operating perfectly.

Hope this helps anyone with a similar issue.

 

Good post...used to wonder why the cold start on my 89 would take so long, drove me nuts.

 

If this is what you believe, once you are assured your relay is functioning properly, start the engine and disconnect the oil pressure switch. Tell us what happens.

 

This part isn't quite right:
In reality, the relay is energized by the ECM for ~2 seconds, key on all the time, hot or cold.
THEN, the relay is energized by the ECM any time there is a crank signal -pulses from the reluctor wheel spinning past the pick up coil, inside the distributor.
Basically, if the crank shaft is turning (and the distributor is turning too), the fuel pump relay should be on. Of course, your car may have had a bad FP relay and sure enough, you found bad contacts. Arbee is right through; you can unplug the oil switch and it should run normally.

 

I'd like to see pictures of what to do here. I have a similar issue and would like to try this solution to see if it helps. Thanks!