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Weird noise and trouble starting

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#1 mushisushi

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Posted 19 December 2016 - 04:31 PM

I've had an issue every winter since I've owned this truck (for the last 3 years) and I haven't yet solved it.


1.5 years ago I replaced the injectors with MPFI to fix hard starting in the summer after the truck has been sitting. I haven't had a single issue this summer with hard starts so that is fixed for sure.


As the weather got colder, I found that trying to start the truck in the morning (temps ~40F) that it will not start on the first try, even after letting the pump prime. After some deliberation, I replaced my noisy old fuel pump with a new Delphi pump which ran silently (nice!). However, this didn't solve the difficulty starting. Didn't have a problem after the winter last year though.


It is now officially winter in Arizona again, and the temps where I am are down in the 30-40s and the same issue has come back. When I prime the pump after the truck has been sitting all night, I hear a weird 'bubbling' noise that seems to come from the engine compartment. I can prime it a few times and the bubbles are present. If I try to start the truck, it stumbles and dies. If I then let it sit for about a minute, and then prime it, I don't hear any bubbles and the truck starts up right away.


What gives?! It sounds like maybe somehow air is in the lines that prevents pressure from building high enough until the air is forced out or something.


I know the go-to test is to test the fuel pressure from the pump and before the plenum. I have done this procedure several times in the last year and a half and I will do so again to give you guys some better ideas, but I always had trouble measuring the fuel pressure at the filter. I used the special fitting with the autozone kit but I can never get the pressure to read on the gauge at the filter. I can only measure the pressure at the plenum where it is in the 55-60 psi range for 10 mins.



#2 eshaw

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Posted 19 December 2016 - 06:46 PM

If it's a percolating type of noise I'd say that the fuel line needs bled.

#3 mushisushi

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Posted 19 December 2016 - 06:51 PM

That's really what it sounds like. How does air get in there? and how do I get it out?

#4 babydeuce

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Posted 19 December 2016 - 08:31 PM

Do you have access to a scanner with live data feed?  I would compare the ECT reading to the AIT reading and to ambient temp.  If the ECT is not reading correctly on the low end, the computer cannot properly set the "richness" of the fuel on the prime command.  Make sense?

#5 mushisushi

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Posted 19 December 2016 - 08:49 PM

I'll give it a go tomorrow morning with the scanner then.

#6 jderekt

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Posted 19 December 2016 - 11:44 PM

I'm with Babydeuce on this one. The symptoms would lead me to the ect.

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#7 mushisushi

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Posted 20 December 2016 - 05:23 PM

Wasn't that cold this morning - ambient temp was 54F, ECT read 59F and AIT read 53.4F.


Truck started first time, though it did almost die, then came back. No bubbling noise today. I did however drive it until 10PM last night.

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