How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Virtual Wrench Your Own Question
Virtual Wrench
Virtual Wrench, Pontiac Mechanic
Category: Pontiac
Satisfied Customers: 14620
Experience:  35 years Master Mechanic
Type Your Pontiac Question Here...
Virtual Wrench is online now
A new question is answered every 9 seconds

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: 2 years ago.
Category: Pontiac
Expert:  Virtual Wrench replied 2 years ago.
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.
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.