My 88 Pickup

V6 - 3vze.

Won't start. It just cranks and cranks and rumbles a little.. and cranks and cranks some more.

I previously thought it was the fuel pump. I was sure of it!
I tested it with a jumper in the .. Fp and E (?) terminals under the hood on the OBD 1.. So.. I replaced the fuel pump and filter. Seems like it needed at least the new filter anyways.

(While diagnosing my issues I also installed a pressure gauge on the fuel line that goes to the cold start, it has helped alot!)

But now.. .. when I test with the terminals under the hood, I do see the fuel pressure go up. About 40 psi.. which is great... but.

Still no fuel when the key is moved to the on position, it only works with the jumper wire.

So I tested the original pump, direct connection to a motorcycle battery. at first there was nothing maybe a slight tap I felt and heard inside the pump but really nothing else. I tapped the probe against the battery terminal a few times and the pump started working.

Was this the issue? ... no(?) ... or not entirely?

The COR Circuit Opening Relay does not click when the key is moved to the On position.

I pulled the COR and tested on the same battery, with a multimeter (continuity mode). COR works fine. The problem is.. I had to look up which contacts were controlling the COR and which terminals the COR control the fuel pump. That's a problem because I was reading no voltage at any terminal in the COR Connector!! .. Key Off or On!!


What to do next..


Actually i'm going to do that test again.

 

Looks like it's not startable with the jumper in place, add to this your pump sticking when directly powered, given those two observations you probably should replace the pump.

It's worth noting the pump doesn't do a prime cycle when the key is turned to on/run and will only activate when the COR gets a start(STA) from the ignition switch or an FC closed from the air meter.

 

I'd have sworn I read that the fuel pump is primed when the key is turned to the On position before starting.. I'd swear I read that multiple places too!

I have replaced the fuel pump tho.

Recently the truck has been starting every time.

 

unless altered from factory, the pumps do not cycle at all with the key turned to the “on” position with the engine note spinning. caveat - the pump should run with the key in the “on” position if the jumper between Fp and B+ is in place, but it won’t cycle, it will run continuously as long as the key is in the “on” or “start” position.