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Virtual Wrench
Virtual Wrench, Pontiac Mechanic
Category: Pontiac
Satisfied Customers: 14618
Experience:  35 years Master Mechanic
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Pontiac Bonneville SE: 3800 engine replaced mass air sensor

Customer Question

3800 engine replaced mass air sensor because it would not start now it starts when cold but will not start when hot and it shows no fault codes ?
Submitted: 1 year ago.
Category: Pontiac
Expert:  Virtual Wrench replied 1 year ago.
Hello,
This has all the symptoms of a failing fuel pump. The pump is an electric motor in the gas tank and when they get hot they slow down and cant make the high fuel pressure needed to work the fuel injectors until it cools down then works until next time. AND it is one of the only things that will not set a code, plus given the fact that these cars are very well known for weak fuel pumps i would have the fuel pressure tested when it wont start and i bet it comes up short. The pressure has to be right at 50-55 psi. Its in your best interest not to buy one from a aftermarket parts store because they all are very low quality and wont last long. Trust me i have seen this 100 times.
LJ
p.s. a little trick you can try is the next time it acts up, take a rubber hammer and smack the bottom of the gas tank and a lot of times it will shock the pump into working for a little while but it still needs replaced.

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