3VZE fuel pump check valve
10-31-2018, 08:11 AM
#1
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Thread Starter
Fuel pump check valve / COR
My 3VZE has similar symptoms to those mentioned in this thread, but only when it is cold. First start of the day on a cold morning, it will crank and attempt to start, maybe run rough at 300-500 rpm for a second and die. On the second attempt it starts and runs fine. When the weather is warm or the truck has already been running previously, it fires right up first try.
I had an opportunity to test what scope103 mentioned in post #10 of that thread today since it was in the 30s this morning. I put a jumper between B+ and Fp in the diagnostic connector, turned the key on for 2-3 seconds and then attempted starting. It fired without issue.
So what I am wondering is would a weak check valve in the fuel pump be more of an issue when the weather is cold since the engine would need more fuel (pressure) to start? Any other ideas?
I tested the CSI and time switch and they appear to be within spec.
I had an opportunity to test what scope103 mentioned in post #10 of that thread today since it was in the 30s this morning. I put a jumper between B+ and Fp in the diagnostic connector, turned the key on for 2-3 seconds and then attempted starting. It fired without issue.
So what I am wondering is would a weak check valve in the fuel pump be more of an issue when the weather is cold since the engine would need more fuel (pressure) to start? Any other ideas?
I tested the CSI and time switch and they appear to be within spec.
Last edited by az4x4runner; 11-01-2018 at 01:10 PM.
10-31-2018, 10:14 PM
#2
Registered User
Thread Starter
Apparently I am wrong about fuel pressure on cold start, per FSM:
Any reason a weak/leaky check valve would cause more issues on a cold morning vs a warm one?
When the engine is hot, the fuel pressure is increased to control percolation in the fuel system and improve restartability and idling stability.
11-01-2018, 12:48 PM
#3
Registered User
Thread Starter
It was about 36 degrees this morning, I jumpered +B and Fp, it started perfectly on the first try. I think I will move on to test the circuit opening relay when I have time before assuming it is the fuel pump.
11-19-2018, 09:36 PM
#4
Registered User
Thread Starter
Update
If anybody is interested in the outcome... the COR tested fine.
Long ago I cut into the FP wire from the COR to install a kill switch. The switch was later removed and the FP wire spliced back together. While I was in there testing the COR, I decided to have a look at my old splice job, I noticed a voltage drop between the splice and the fuel pump while cranking. I cut out the old butt connectors, cleaned everything up, installed a new heat shrink butt connector and I haven't had a problem since. I guess only time will tell, but I can't find anything else electrically wrong, so maybe this really is it...
Long ago I cut into the FP wire from the COR to install a kill switch. The switch was later removed and the FP wire spliced back together. While I was in there testing the COR, I decided to have a look at my old splice job, I noticed a voltage drop between the splice and the fuel pump while cranking. I cut out the old butt connectors, cleaned everything up, installed a new heat shrink butt connector and I haven't had a problem since. I guess only time will tell, but I can't find anything else electrically wrong, so maybe this really is it...
Last edited by az4x4runner; 11-19-2018 at 09:40 PM.
11-20-2018, 10:56 AM
#5
Registered User
Thanks for the update! It helps people who come across this thread in the future.
It sounds like you fixed the problem.
Even if the problem returns, you have at least fixed a known issue as shown with the voltage drop.
It sounds like you fixed the problem.
Even if the problem returns, you have at least fixed a known issue as shown with the voltage drop.
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saltandgranite
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