Fuel Pumps Keep Running
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Fuel Pumps Keep Running
This forum has saved me lots of dollars, time and angst over the years but I have a problem now which has stumped me even after reading all the appropriate threads and I need to post with the hopes that you experts out there can help me, yet again.
Here's my scenario: '89 F250 4.9 Litre with dual tanks and the fuel pumps won't stop running. If everything is plugged in, the truck will start and run for 30 seconds and to try to figure out the problem I've done the following:
1. Unplugged the EEC relay, fuel pump relay and the PCM plug. The only thing that will shut the pumps off is triggering the inertia switch or pulling the ground off the battery.
2. Have isolated the front tank with a single tank reservoir to alleviate the possibility of a 6-port fuel valve failure.
My questions are: if the fuel pumps were even hard wired to the starter relay, why won't the truck stay running? Am I on the right track? Should I be concerned about the in-tank fuel pumps not shutting off?
The next post is going to be to the wrecker.
Here's my scenario: '89 F250 4.9 Litre with dual tanks and the fuel pumps won't stop running. If everything is plugged in, the truck will start and run for 30 seconds and to try to figure out the problem I've done the following:
1. Unplugged the EEC relay, fuel pump relay and the PCM plug. The only thing that will shut the pumps off is triggering the inertia switch or pulling the ground off the battery.
2. Have isolated the front tank with a single tank reservoir to alleviate the possibility of a 6-port fuel valve failure.
My questions are: if the fuel pumps were even hard wired to the starter relay, why won't the truck stay running? Am I on the right track? Should I be concerned about the in-tank fuel pumps not shutting off?
The next post is going to be to the wrecker.
Fleet Owner
Joined: Aug 2005
Posts: 23,666
Likes: 301
From: Easton,Ks
The ECM/PCM will not keep the fuel pumps running if the fuel pump or the EEC Power relay is pulled like he did.
Someone has rewired the trucks fuel system.
If the truck runs for 30 seconds and then quits it could be the ECM/PCM but more than likely the TFI (ICM) on the side of the distributor.
Could also be the PIP sensor in the distributor or the coil but check the TFI (ICM) first.
Then if it does not start after it quits:
Is the injectors firing?
Do you have spark?
Can you get any codes?
Someone has rewired the trucks fuel system.
If the truck runs for 30 seconds and then quits it could be the ECM/PCM but more than likely the TFI (ICM) on the side of the distributor.
Could also be the PIP sensor in the distributor or the coil but check the TFI (ICM) first.
Then if it does not start after it quits:
Is the injectors firing?
Do you have spark?
Can you get any codes?
Cargo Master
Joined: Nov 2013
Posts: 2,168
Likes: 3
From: South Central,MO
On my 90, there was a little piece of the relay plug broken out and the wires welded themselves together so even when you pulled the relay the pump still ran. But the truck ran fine, just drained the battery overnight. Sounds like you have more problems.
Postmaster
Joined: Nov 2011
Posts: 3,533
Likes: 17
From: SW Florida
... I missed where he mentioned pulling the fuel pump relay already.
So you're saying that the pumps run continuously with the engine off, but when you start the engine, it runs for a bit and then dies?
Are the fuel pumps still running when and after it dies?
So you're saying that the pumps run continuously with the engine off, but when you start the engine, it runs for a bit and then dies?
Are the fuel pumps still running when and after it dies?
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Mountain Pass
Joined: Jan 2014
Posts: 214
Likes: 37
From: Madison Ohio
Check the fuel pump relay socket. make sure Its not corroded and split some. I have seen a couple here in the road salt country that the plastic split between pins and shorted. If looks good there pop the trim off that holds your tank switch in place and make sure nothing is melted, shorted, or jumped there. After that your going to have to trace wires under to find the damage or jumped wires.
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Thanks for all your replies.
Dixie 460: Yes. The pumps are still running when the engine dies.
Update: I went to pull the TFI. Turns out I don't have a 5.5 ml socket. I'm leaning towards Subford's recommendation and am going to replace the TFI. Fingers crossed. I'll keep you posted. Hopefully I'll be driving around tomorrow at this time. Gotta get off that motorcycle. It's cold up here and rain is coming.
Dixie 460: Yes. The pumps are still running when the engine dies.
Update: I went to pull the TFI. Turns out I don't have a 5.5 ml socket. I'm leaning towards Subford's recommendation and am going to replace the TFI. Fingers crossed. I'll keep you posted. Hopefully I'll be driving around tomorrow at this time. Gotta get off that motorcycle. It's cold up here and rain is coming.
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Chalk another one up for Subford! You hit the nail on the head with the TFI. It fired up and runs like a champ.
One last question: does anyone have any idea why somebody would want to hardwire the fuel pumps as I can still not figure out how to get them to shut off after the initial key on sequence
Thanks again.
One last question: does anyone have any idea why somebody would want to hardwire the fuel pumps as I can still not figure out how to get them to shut off after the initial key on sequence
Thanks again.
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