Another "Won't Start" Thread

[jt_armstrong]

This morning I decided to use my wife's expy (2003 4.6) to go to work. I haven't driven it for a while and it was nice. I came home for lunch and 40 mins later went to go back to work only it wouldn't start. At first it started but struggled to get beyond 200 rpm before dying. Same thing happened a second and third time. Forth time it just would not fire at all.
I didnt have time to troubleshoot as I had to get back to the office.
Got home this evening and went out ready to start a methodical troubleshooting process only she started right up first time with no issues.
My initial thoughts are fuel pump related but how can I test that theory with out swapping the pump?
Any ideas?

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[stamp11127]

Take fuel pressure readings.

 

[jt_armstrong]

Take fuel pressure readings.

Do you mean the next time it doesn't start or would I get some indication of a failing pump from the fuel pressure even if it primes ands starts?

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[stamp11127]

Fuel pressure readings can give both. It will also show how long it takes to pressurize the fuel rail(if it bleeds down) and operating pressure.

 

[jt_armstrong]

Hi so I managed to get a fuel pressure tester. Here are the 3 readings I took.
1) Engine off - ignition off -5psi
2) Engine off - ignition on - 28psi
3) Engine on (Idle) - 48 psi.

Does this tell me anything useful?

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[Hamfisted]

How old is the fuel filter ? Might be a flow problem too. If the filter is 3 years old or more I would change it. Are you getting any check engine light ? The '03-'06s also had a problem with the micro fuel pump relay there in the fuse box circuit board. So if you start hearing a buzzing from the fuse box that's what that is.


-Mike

 

[stamp11127]

+
The 5 psi reading is telling you the fuel system is bleeding down over time. The 28 psi reading is a little low but the 48 psi is fine.

How long did it take to get up to the 28 psi?

All it means at this point is there is some wear and tear on the pump. I would replace it as a maintenance item dependant on mileage. I normally replace mine when they get 150,000+ on them.

How many miles are on the clock?

I would also pull the fuse block and check the fuel pump relay. That will require opening up the fuse box to inspect the board and clips. If you do it, take a picture of the fuses so that you can reinstall them in the correct spot.

 

[jt_armstrong]

+
The 5 psi reading is telling you the fuel system is bleeding down over time. The 28 psi reading is a little low but the 48 psi is fine.

How long did it take to get up to the 28 psi?

All it means at this point is there is some wear and tear on the pump. I would replace it as a maintenance item dependant on mileage. I normally replace mine when they get 150,000+ on them.

How many miles are on the clock?

I would also pull the fuse block and check the fuel pump relay. That will require opening up the fuse box to inspect the board and clips. If you do it, take a picture of the fuses so that you can reinstall them in the correct spot.

She had been sitting for a couple of days while I found a tester. The pressure jumped to 28 in less time than it took me to turn the ignition on and walk round to the tester. A couple of seconds at most.
There is only 122K on the clock - not sure if it is worth dropping the tank and swapping out the pump.

 

[stamp11127]

The next time it stalls check the fuel pressure without cycling the ignition key. If it is less than 35 psi it is a fuel related issue.
I would hold off on the pump until after checking the fuse box.

 

[jt_armstrong]

OK, thanks for that. I need to do some research on the fuse box issue.

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