Need help diagnosing fuel pump issue

M

MountainBrew

New member
Good afternoon all,

I don't want to rehash a worn out topic, but I've been searching the forum for several hours now and haven't come across a solution.

98 4Runner Limited 3.4 300,000mi

Long story short, I've been welding together armor for my new-to-me 4R. It's been up on jacks for the last week or so while I fab the skids and bumpers. Since I got it I've had no starting or running issues at all.

Today I reconnected the battery and tried to start, cranks fine but no start. I noticed no sound at all coming from the fuel pump.

Any thoughts on what might have caused this? I've had absolutely no issues with the fuel pump up to this point so I doubt it is a coincidence that I've done all this work on it

Thanks in advance
 
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MountainBrew said:
Good afternoon all,

I don't want to rehash a worn out topic, but I've been searching the forum for several hours now and haven't come across a solution.

98 4Runner Limited 3.4 300,000mi

Long story short, I've been welding together armor for my new-to-me 4R. It's been up on jacks for the last week or so while I fab the skids and bumpers. Since I got it I've had no starting or running issues at all.

Today I reconnected the battery and tried to start, cranks fine but no start. I noticed no sound at all coming from the fuel pump.

Any thoughts on what might have caused this? I've had absolutely no issues with the fuel pump up to this point so I doubt it is a coincidence that I've done all this work on it

Thanks in advance
Click to expand...
Fuse, perhaps?
 
Fuel pump only pumps when engine is turning. Doesn’t pump up at key on like most rigs.

Were you welding on the rig?

Crank position sensor can give a no start and no engine code when it dies.

You could crack a fuel line fitting and see if there is residual pressure after cranking a bit. These rigs don’t have a Schader valve.
 
Dieselchessy said:
Fuel pump only pumps when engine is turning. Doesn’t pump up at key on like most rigs.

Were you welding on the rig?

Crank position sensor can give a no start and no engine code when it dies.

You could crack a fuel line fitting and see if there is residual pressure after cranking a bit. These rigs don’t have a Schader valve.
Click to expand...


Well then I’m not sure what the problem is, I read in a bunch of threads that the fuel pump runs at key on before ignition so that’s why I assumed fuel pump issue. If that’s not the case it could be something else.
I was tack welding on the rig


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I checked all the relays, jumped the +b fp, did every test I could find on the forum. Went back to the fuel tank access panel which I had already checked and it turned out the connector had separated in the middle along the horizontal seam. This had been exacerbated by the 1” BL I installed a few weeks ago (don’t judge, kids at the mall we’re making fun of my stocker) which strained the wiring harness and separated the connector. It wasn’t visible at first glance. After fixing it fired right up.

Thanks for the suggestions


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