'03 4.2L manual tans. intermittent low fuel pressure
11-29-2013, 05:25 PM
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'03 4.2L manual tans. intermittent low fuel pressure
Truck has single gas tank.
In a nutshell: If the truck sits for a few hours, it starts right up. I can drive as many miles as I want without a problem. Buuuut, when I turn the truck off after a drive, I try to restart it right after I shut it off and no dice. The motor turns over fine, but no firing. Let it sit for a couple hours, fires right back up.
After a ride, turned it off and of course it wouldn't restart 2 minutes later. Had someone push the needle on the Schrader valve while I turned the key. I heard the fuel pump kick in. Turned the motor over & Fuel did come out, but he guessed it was 15-20 psi. He said it should be SPRAYING outta there. Not enough pressure to get the injectors to open. When it IS running, I notice a rise in rpms when I shift to neutral and slowing down for a stop. Not drastic, but its noticeable. When i'm nearly stopped (the last 4-5' of coasting) I hear the rpms drop to a normal idle.
I just put a new fuel filter on. Didn't fix the problem. Fuel pump replacement time, or something else to check before I buy an new pump?
In a nutshell: If the truck sits for a few hours, it starts right up. I can drive as many miles as I want without a problem. Buuuut, when I turn the truck off after a drive, I try to restart it right after I shut it off and no dice. The motor turns over fine, but no firing. Let it sit for a couple hours, fires right back up.
After a ride, turned it off and of course it wouldn't restart 2 minutes later. Had someone push the needle on the Schrader valve while I turned the key. I heard the fuel pump kick in. Turned the motor over & Fuel did come out, but he guessed it was 15-20 psi. He said it should be SPRAYING outta there. Not enough pressure to get the injectors to open. When it IS running, I notice a rise in rpms when I shift to neutral and slowing down for a stop. Not drastic, but its noticeable. When i'm nearly stopped (the last 4-5' of coasting) I hear the rpms drop to a normal idle.
I just put a new fuel filter on. Didn't fix the problem. Fuel pump replacement time, or something else to check before I buy an new pump?
Last edited by ausablejunkie71; 11-29-2013 at 05:35 PM.
12-03-2013, 01:44 AM
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After doing more post reading here, I figured out the FPDM isn't on my 2003 truck. If there's a "search this forum" option here, 'guess I missed it. I bought a new fuel pump today (with new relay on it) and hope that does the trick.
12-18-2013, 09:20 AM
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The follow up:
I had a new fuel pump put in it. It didn't solve my problem. After more time troubleshooting, my mechanic figured it out. The coolant temperature sensor had gone bad. A $20 part versus a $200 fuel pump.
To be fair, I bought the new pump and told him to put it in without asking him to do any trouble shooting, so its not his fault I paid for a pump I didn't need.
The bad sensor was telling the computer that my truck was cold, regardless if it was cold or had just run 100 miles. That's why it started up after sitting a long time. When I ran it & shut it off, it failed to restart because the computer thought the engine was cold. The large amount of gas being delivered for the "cold start" was flooding my engine.
I posted this follow up so anyone coming here with the same problem might see my solution and be helped by it. I get the feeling new members on this forum might not get the support of the regulars here. My thread had 129 views without any suggestions or comments.
To be fair, I bought the new pump and told him to put it in without asking him to do any trouble shooting, so its not his fault I paid for a pump I didn't need.
The bad sensor was telling the computer that my truck was cold, regardless if it was cold or had just run 100 miles. That's why it started up after sitting a long time. When I ran it & shut it off, it failed to restart because the computer thought the engine was cold. The large amount of gas being delivered for the "cold start" was flooding my engine.
I posted this follow up so anyone coming here with the same problem might see my solution and be helped by it. I get the feeling new members on this forum might not get the support of the regulars here. My thread had 129 views without any suggestions or comments.