truck cranking but not starting
12-15-2013, 11:30 AM
#1
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truck cranking but not starting
I have a 1990 Toyota 3.0 6cin 4x4 pickup
Truck will crank and start at different times after driving for a while.
Replaced fuel pump. fuel filter and fuel regulator but still won't start at different times after driving.
If I remove the rubber hose from the fuel regulator and just turn the key to crank for a second, to allow some fuel to come out, hook the hose back up and it will start sometimes. Then sometimes I just let it sit and then it starts. Not sure what else to do.
Any assistance would be appreciated.
Truck will crank and start at different times after driving for a while.
Replaced fuel pump. fuel filter and fuel regulator but still won't start at different times after driving.
If I remove the rubber hose from the fuel regulator and just turn the key to crank for a second, to allow some fuel to come out, hook the hose back up and it will start sometimes. Then sometimes I just let it sit and then it starts. Not sure what else to do.
Any assistance would be appreciated.
Last edited by two feathers; 12-17-2013 at 06:05 AM.
12-17-2013, 11:28 AM
#2
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Most likely it's not fuel related, directly. The VAFM sends a signal to the fuel pump when cranking, if that wire is damaged or the VAFM is failing, it does not send the signal and the fuel pump will never turn on. That's how I wired my kill switch 
.
Check your VAFM per the service manual using a multimeter. If if checks out ok, search the forums. There's been a lot of these lately and I'm sure someone has posted your fix.
.Check your VAFM per the service manual using a multimeter. If if checks out ok, search the forums. There's been a lot of these lately and I'm sure someone has posted your fix.
12-17-2013, 11:34 AM
#3
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easy way to test that is jump the FP diagnostic. It will make the pump run as soon as you turn the key to the on position. If it starts up everytime with that jumpered then its likely what gamfreak said, wiring in the VAFM or the VAFM itself. I do not recommend driving the truck with that jumpered, if you get in an accident or anything goes wrong that fuel pump will run continually until the key is off.
12-17-2013, 04:50 PM
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Look into your Fuel Pressure Up (FPU) system. http://personal.utulsa.edu/~nathan-b...ne/99fuelp.pdf To prevent vapor lock, when the engine is warm the ECU raises the pressure in the fuel rail. How does it do it? The VSV effectively disconnects the vacuum line to the Fuel Pressure Regulator. Sound familiar? (Actually, I think the rubber hose you're removing is the fuel return line, not the vacuum line, but vapor lock could be your problem.)
It's probably not your VAF; if that failed you should have a starts-fine-but-won't-stay running problem (that's why it works so well as a kill switch!)
It's probably not your VAF; if that failed you should have a starts-fine-but-won't-stay running problem (that's why it works so well as a kill switch!)
09-12-2014, 02:36 AM
#6
Thanks for following up, I'm going to check mine tomorrow- been having a minor starting issue myself and it is very intermittent.
Had an issue with some new spark wires a few weeks ago and it was around the same time that I started having problems. Here this whole time I thought it was a fuel issue and it might just be ignition related. Thanks again
Had an issue with some new spark wires a few weeks ago and it was around the same time that I started having problems. Here this whole time I thought it was a fuel issue and it might just be ignition related. Thanks again
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