Bad Fuel Pump or Something Else?

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Hey all,

My 1992 FJ80 has been having some trouble starting. It takes a bit of time and when it does turn over, the rpm's are low (200's) until I give it some throttle. I've done the easy stuff (new battery, new plugs, cap and rotor, new fuel filter, new EGR modulator, and new air filter). I had a feeling it might have a bad fuel pump so I got a test kit and hooked it up.

When I flip the key on, there is no pressure. Zero. But when I try to crank, it fires up, eventually with some assistance from the throttle. Still no pressure on the gauge. Then over time, the pressure will build. The longer I keep it running, the higher the PSI goes until it reaches ~40psi.

I attached the test gauge on the cold start injector at the top of the intake manifold. Would this be a bad fuel pump or is the problem somewhere else? Maybe I'm not testing the pressure properly?

Appreciate the help, thanks!
 

Tools R Us

 
 
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The fuel pump doesn't come on till the starter is cranked. What happens when the fuel pump is jumped at the diagnostic connector, is it the same or a faster pressure build?
 
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I haven't done the test with the jumper. How should I go about it? Start the engine with the jump and see the build then remove?
 

Tools R Us

 
 
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Not sure about the early, 3FE wiring, but when the key is turned to run, the pump should run. Maybe try just turning to run, then repeat when starting?
 

SUMMIT CRUISERS

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Three items come to mind. Fuel pump and or fuel sock/strainer, pressure regulator and lastly the damper. I would start with the sock/strainer, then regulator lastly damper and fuel pump.
If these have never been changed, your truck being 27 years old probably needs some love in these fuel system items.
 

jonheld

 
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If you jump pin 8 (B+) to pin 1 (FP) on the diagnostic connector on the firewall, the FP will run as soon as the key is in the ON/RUN position. However, it is unlikely that the FP is the issue in your case. As previously stated, if you haven't addressed the maintenance items in the fuel system in 27 years, it might be time.

CheckConnector.jpg
 
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Thanks for the advice guys. I now understand the point of the jumper cable! :D

Regarding replacing the fuel sock, pressure regulator, and damper, should I replace all at once? Or try to narrow down the problem parts? I would hate to throw the 2nd row seats on after changing the sock, only to need to replace the fuel pump 2 months from now.

Out of curiosity, do fuel pumps die suddenly or do they start giving problems before?
 

flintknapper

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Thanks for the advice guys. I now understand the point of the jumper cable! :D

Regarding replacing the fuel sock, pressure regulator, and damper, should I replace all at once? Or try to narrow down the problem parts? I would hate to throw the 2nd row seats on after changing the sock, only to need to replace the fuel pump 2 months from now.

Out of curiosity, do fuel pumps die suddenly or do they start giving problems before?
Yes, if your wallet will stand it....just replace all at once. The time spent chasing down the issue on a vehicle that old isn't worth it...since it isn't at a shop being charged shop rates. Fuel pumps CAN die either way (all at once or show signs). The vast majority of pumps in Land Cruisers die a soft death (exhibit signs). Tell-Tale sign is that your pump takes time to build up pressure.

If it were me...I'd check my wiring first (make SURE you have proper voltage everywhere) and IF that proved out, just refresh your fuel system. Pump, new sock, fuel filter, PR and Damper. Drive it another 20 years.
 
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Yes, if your wallet will stand it....just replace all at once. The time spent chasing down the issue on a vehicle that old isn't worth it...since it isn't at a shop being charged shop rates. Fuel pumps CAN die either way (all at once or show signs). The vast majority of pumps in Land Cruisers die a soft death (exhibit signs). Tell-Tale sign is that your pump takes time to build up pressure.

If it were me...I'd check my wiring first (make SURE you have proper voltage everywhere) and IF that proved out, just refresh your fuel system. Pump, new sock, fuel filter, PR and Damper. Drive it another 20 years.
Gotcha, thanks for that.

Do you mean to check the entire truck's wiring or only relating to the fuel system? I haven't experienced any signs of an electrical issue (to my knowledge). I have the Haynes and Chilton books as references. They have a lot of wiring diagrams and such. Maybe go through those?
 

flintknapper

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Gotcha, thanks for that.

Do you mean to check the entire truck's wiring or only relating to the fuel system? I haven't experienced any signs of an electrical issue (to my knowledge). I have the Haynes and Chilton books as references. They have a lot of wiring diagrams and such. Maybe go through those?
Wiring to/at the fuel pump and the connectors there. It would be fruitless to replace the other parts IF your issue were actually electrical (poor connection, corrosion, ground, resistance,relay). There is a procedure for checking this in the FSM.
 
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I'm not an expert in this area, but could the fuel pump relay be bad or failing intermittently? Mine was failing intermittently and the symptoms were it started sometimes and ran fine, and other times would not start. As I write this, that seems quite different than your symptoms. In any case, I thought I'd just add that thought because it is a mission critical part in the electrical/fuel system, which does fail with time. It's about $90 at the dealership (there are aftermarket options for less dough). If you're goal is to have replaced all potential failure points in the system, I'd suggest considering the fuel pump relay. Just a thought.
Good luck.
 
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Hey guys, so I finally got around to replacing some parts and I'm having some trouble with the damper. I got the old one off, but I am really struggling to install the new one. The main issue is a wiring harness that is in the way preventing me from starting to thread the part properly. Does any one have any tips on how to make this easier?
 
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