Help Troubleshooting a Fuel Issue (1 Viewer)

[ElPolloBlanco]

I need help troubleshooting what I think is a fuel issue. For a while now my rig has acted strangely during acceleration. You push the gas, it starts to accelerate, then does what I can only describe as "bog" down. It's like a loss of power, the engine is still running but there is not power. It then picks back up and runs fine. It usually does this when I'm leaving my house, ie the engine is cold.

Here lately, it's been warm, but I'm not sure if that even plays a part. I stopped at a convenience store the other day and when I came back out it seemed like the engine wasn't getting fuel. It kicked over then died almost immediately. I then cranked on it and cranked on it and it wouldn't start. After a few minutes I turned it over, giving it some gas, and it started up but had a rough idle for a few seconds.

I have the inside torn apart for another project, So i took the pump and stuff out. The sock has a little bit if dirt in it, but nothing crazy. I'm thinking my fuel pump is going out and having a hard time keeping up with demand during start up and acceleration. Is there a good way to test this? Where else should I look before buying a new pump? And is there any type of upgrade I can do to the pump while it's out?

thanks

 

[Formulaonehd]

- Fuel pump might be history (good preventative maintenance to replace)
- Bogging down may be a spark issue, replace them/check em and your leads. Does it sound like its firing on 5 cylinders ?
- Injectors might also be blocked. The injector fuel cleaner may also clear this up without needing replacing

 

[ajax1]

Fuel pump relay and reister should be changed out they control switching from high to low demand on the fuel pump, I had hard starting like you describe, I did few things which was relay and resister, fuel pump, bought denso from rock auto was plug in play comes with sock for 112.00, then found bad vacuum lines under the manifold. I got rid of the vacuum lines and all the vacuum switches under the manifold. I also have obd1 so no codes from doing all that. The only vacuum line I have is to the fuel pressure regulator on the fuel rail.

 

[blkprj80]

The FSM says to check the resistance of the fuel pump. 0.2 to 3.0 ohms is good. Other than that, if it runs, it's good I guess.

Your problem sounds like a typical clogged fuel filter.

I'd then check the fuel pressure regulator at the front of the intake manifold, and the fuel pump relay / resistor. The fuel pump relay / resistor (I think) kicks in when you ask for extra fuel, like accelerating.

I hope you find a simple fix. If you replace the fuel pump, it may not solve the problem. That said, I'd probably put in a new one if it was 300K miles or more. That's a lot of fuel.

Good Luck!

 

[ElPolloBlanco]

I'm at about 155,000 miles. I'll dig into the relay when I get my next day off (I work 12 hour shifts) where would I go looking for that at? Also, is it just a generic denso pump if I need it? I called Orielly for a replacement and they said $251. Might need a new filter. The tank looks clean and the dirt on the sock was minimal.

 

[Formulaonehd]

I'm at about 155,000 miles. I'll dig into the relay when I get my next day off (I work 12 hour shifts) where would I go looking for that at? Also, is it just a generic denso pump if I need it? I called Orielly for a replacement and they said $251. Might need a new filter. The tank looks clean and the dirt on the sock was minimal.

This is a good thread for references

Emergency Troubleshooting Procedures - FAQ Item (Recommend Keeping Copy in Truck)

 

[Rifleman]

Do the simple things first, put a new fuel filter on it, I've got a feeling that's going to take care of your problem.

 

[SUMMIT CRUISERS]

Do the simple things first, put a new fuel filter on it, I've got a feeling that's going to take care of your problem.

Do this and change the fuel pump sock, especially if the sock has not been ever changed and it looks like it has been sucked in. It also could a vacuum leak. Check intake hose and all vacuum lines for cracks.

 

[Malleus]

This information is obviously not from your year model FSM, but it does show where the relay and resistor are, and what they look like. The best resource available is the TIS downloadable FSM (best $15 you'll spend on your truck).
https://techinfo.toyota.com/techInf...nfpb=true&_pageLabel=ti_home_search_docs_page

 

[ElPolloBlanco]

I have the 96 manual I got when I had my 96. I tested the pump like the FSM says and I got .9 ohms so I think the pump is good. But then again the error is intermittent. I'm going to reinstall the pump everything and work forward fr M there. I also wanted to just make sure there wasn't something in the tank hindering flow. Going to check the relay next.

 

[Malleus]

FWIW, that would be my troubleshooting logic too. Another poster had a similar situation a couple of days ago. Might be worth looking at.

Fuel pump relay -continuity specs?

 

[alia176]

Try not to throw parts at the problem, use this board to troubleshoot the problem step by step. And Please, update us on what you've tried thus far so that we don't have to read the whole thread to get up to speed. We'll help you figure it out, no worries.

 

[ElPolloBlanco]

I found a thread on repairing the relay by sanding down the contacts inside of it. I'll have to search for it again. I'm going to give that a shot. I think my behavior is more indicative of the FPR being bad. Like maybe the rely isn't gettin good contact. It would make sense with the fact it may not be sending 12v to the pump on start up and during initial acceleration it's not sending the 12v to the pump. I'll have to do it when I get done with my current wiring project.

 

[Tools R Us]

The down and dirty fuel pump power supply test: Make a jumper wire to go from the B+ terminal in the diagnostic connector to terminal #3 (R/B wire) on the fuel pump relay socket. This will run the pump at full speed when the key is on, if the problem doesn't happen with the jumper, it's one of the relays, fuses, etc. The other thing we have done; take the cover off of the relay and manually operate it, sometimes will work one way and not the other.

Have not had good results with sanding/reviving them. IIRC, rockauto.com has the Denso for ~$45.

 

[blkprj80]

As @Malleus link shows, the relay is behind the ABS junk, and the resistor is over on the other side behind the cruise control. The resistor has cooling fins on it.
Sometimes just unseating and reseating a relay will get it to start working again, if the contacts in the plug socket are dirty. I had an ABS problem that went away after I wiggled only the relay.

 

[ElPolloBlanco]

From @Malleus 's link

Hmm, might want to check for a bad fuel pump resistor as well. Symptom will be starts but then dies after about 3 seconds. Easy to check, its a small aluminum box with cooling fins mounted to the passenger side inner fender. To check, unplug and using a paper clip, jump the terminals on the harness side of the plug and see if that fixes the problem.

I have this problem sometimes too, which I think could also be attributed to the relay if it's not sending the 12v signal at startup (ie pump isn't keeping up with demand). I'll try both. @Tools R Us are you talking about the diagnostic plug on the passenger side on the firewall?

I should also mention that on very very rare occasion the rig will die at red lights, but if I mess with the throttle it will continue to run.

 

[Tools R Us]

... @Tools R Us are you talking about the diagnostic plug on the passenger side on the firewall?
...

Yep.