So, 86, EFI 302. turn the key and sometimes the fuel pump keeps running and won't start. Other times turn the key listen and the fuel pump turns off in the normal amount of time and starts. New relays and wiring harness/ pigtail. Yes soldered in. single tank. new fuel filter.

 

When the pump runs and will not start are you getting spark at the plug?
I would think as long as the pump is running and you are getting spark it would run.

Now I dont know the EFI system like others but the key on run for a short time I think it sent from the computer no?
I would think you need to see when the pumps run with key on if the relays are getting a signal to do so or they getting power from somewhere else?
I also wonder if what the pump runs and will not start besides spark if the injectors are working like they should?
If pump is running and you got spark but no run then injectors may not be working and that might be a computer thing?
Computer ground clean and maybe look at the caps inside?
That is all I got.
Dave ----

 

Isn't the fuel pump supposed to run for a few seconds and then shut off until you completely start the truck? I am turning it on and not starting it. If I turn it on and the pump runs for a few second and then I go to start it, it starts. I turn it on and not start it and the pump just keeps running and i try to start it it will just keep cranking.

 

Again I am no pro in the EFI stuff but you are right from what I have seen posted.
Key on pump run for a few seconds to prim system but shut off if motor not running.
If the pump is staying running longer then you need to find why.
Is the relay stuck, yes even new can or is it getting a signal from the computer to stay running?

Think easy to check if getting signal with a test light at the relay.
If it is getting a signal then why that is the hard part and someone else will need to jump in.
Dave ----

 

I heard that the fuel pressure regulator is failing possibly. I have another one and have not had the time yet to replace it.

 

You want to replace the FPR because the pump keeps running SOME TIMES when the key is on?
The FPR job it to keep the PSI at a set PSI it has nothing to do with the pumps running when they should not be.
As far as I know there is no PSI switch that tells the computer to turn the pumps off when it reaches the set PSI, it is a timing thing from what I know.

To test the FPR you need to hook up a fuel PSI gauge to the system and turn the key on and see what it reads.
Then start the motor and see what it reads. I would also bring the RPM up and see what it reads.
I dont know what the limits are but if with in the spec the FPR is good.

The other thing if you pull the hose off and it has fuel in the hose then yes it is bad and needs to be replaced.
But from what I seen posted if there if fuel in the hose the PSI will be out of spec.
Dave ----

 

fuel pressure reg. is on the fuel rail close to the fire wall

 

I believe it is with a vacuum hose to it but I am not up on the EFI stuff like others are.
But I do know the FPR has nothing to do with the pumps running when they should not or how long.
DaveF & Karl where are you guys
Dave ----

 

Here's the FPR,

 

I also just went out and checked mine. I had to buckle the seatbelt before I could hear the pump. After getting in and buckling up, turn the key to On, fuel pump runs for a second and stops. You can hear the hum.

I normally hold the key in On for a second or two, before starting the engine for the first time that day. I don't drive the truck much, so to me, it makes sense to prime the fuel pump.

 

Sounds like you have a electrical problem, not a fuel pressure regulator problem. I think I would find the fuel pump relay and see what condition it is in. You might have another relay under the hood you could swap it with, like the WOT A/C relay or possibly the horn relay. I think the EEC power relay is the same.

 

I replaced the relay and the harness / pigtail for it. I'll switch it out with another one to see. thanks for the info

 

@86EFI5.0
Fuel pump operation: key turns on and EEC commands pump to run for about one second. A fuel delivery system in good order will fully pressurize in that one second. Key turned to start and fuel pump runs and continues to run as long as you're cranking and stays running when the engine runs.

On the four wire relay, the yellow is always hot.

Key off, only yellow is hot.

Key on/not running, no pump (after one second) Red, yellow, tan/light green hot. Pink/black not hot

Cranking, running Red, tan/light green, pink/black hot. Pump is running. Tan/light green not hot.

Relay: yellow is always hot power supply to relay switch circuit from blue fusible link for pumps. Pink/black is power from relay to the pumps.
Red is power to relay solenoid from EEC. Tan/light green is solenoid ground to EEC. EEC internally grounds relay solenoid to close pump power switch.

So, if pump runs with key on and engine off, it is possible that the tan/light green wire has an intermittent short to ground. (Deleted some opinion here that didn't add up after sleeping on it)

​The tan/light green wire that is questionable in this scenario is connected to the EEC on post 22, middle row, second from end. Second from end on opposite end of the row has no wire so there's no confusion.


Other possibilities include sticking relay, either solenoid or switch. Bad EEC.

As mentioned, the FPR has nothing to do with the pumps running or not.

 

I wish you were closer to NW Indiana. Lol thanks for the info. I'll check for a short.

 

could the ignition switch be part of the problem? Thanks for the help. EEC is new and only one tank on the truck.