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Bob
Bob, Auto Service Technician
Category: Car
Satisfied Customers: 4087
Experience:  40 year GM Tech. +30 Certified. ASE Master Tech.(expired, retired) Medium Duty, Heavy Line, Retired
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2002 Buick Rendezvous: starting problems..it wont start..errands..bus

Resolved Question:

Hello. I have a 2002 Buick Rendezvous. Within the last year we have had starting problems, where it won't start even after having run errands all day or just going to the bus stop and back again. It is very sporadic. We have had the fuel injection module replaced and the fuel pump replaced for a total of $1400 and it still has the same problem. When we move it to have it towed it will start up before being loaded up or when it is towed to the dealership it will start right up. We have also had the main computer module replaced. I actually got in the back of the SUV and jumped up and down to get the fuel tank moving and it cranked right up. It will try to turn over but will not fire up like there is no gas getting to the engine. Is this strictly some unkown electrical bug, or is it something do with the fuel tank such as contaminants or the fuel level sensor? Thanks.
Submitted: 5 years ago.
Category: Car
Expert:  Bob replied 5 years ago.
Hello, hate to say it, but there is a good possibility that you have a problem with the fuel pump. If you can get the car to act up long enough to do a pressure test on the fuel system, it would not be hard to verify. I had a laugh at the jumping up and down to make the tank move as that is one of the things we sometimes do to get a lazy pump to work again for a short time. A good wrap on the bottom of the tank with a rubber hammer will sometimes get a lazy pump going again. If you take the gas cap off when the car will not start and listen for the hum of the pump inside of the tank, it should make noise and run for the first 2 seconds when the key is turned on. Then the pump should also run all of the time when the starter motor is being engaged on the car. You should also have voltage to the gray wire that goes to the top of the fuel tank during those times. 2 seconds at key up, all the time when cranking. And you should be able to hear the pump running. If you have voltage and no pump action, replace the pump. If you do not have voltage, then we need to do some further testing. BUt, you can also use a spray can of starting fluid to verify a lack of fuel problem. If you spray a shot of starting fluid into the intake and the car fires right up, then you know it is a fuel delivery problem. If that does not help, you can remove a couple of spark plugs and lay them on the motor so they have a ground and then with the wires still connected have someone crank the motor over while you watch the plugs to see if they have good hot spark while cranking. If they do, then the ignition system is ok. Let me know what you find and we will go from there. The specs for the fuel pump pressure are 52 to 59 psi and it should not loose more than 5 psi in 5 minutes setting. Any thing under 52 psi could keep it from running. Thanks
Customer: replied 5 years ago.
The techs where I take my car say they can't reproduce the problem, so they can't figure out what is wrong when they do a diagnostics check. They say that the fuel pump is ok and everything checks out supposedly. Is it possible that the fuel pump they put in August '08 could be bad? How would they know if the fuel pump is not working properly if when the SUV is working the fuel pump pressure is ok? Thanks for your help.
Expert:  Bob replied 5 years ago.

Yes, it is possible that the new fuel pump is bad. Many times they will have an intermittent problem and work for a while and then stop, only to keep repeating the process. If I was working on the car and had an doubts about the pump, I would install a fuel pressure gage on it in such a manner that you could monitor it from the drivers seat. Maybe duct tape it to the windshield wiper arm or something similar. Then you could drive the car and when it acts up you could look at the gage and see if the pressure had gone away or not. It might not look good, but sometimes you have to go to extra lengths, just to get a good diagnosis done. You could do the same thing with the ignition system. Connect a volt meter to the main power leads going to the coil pack or module and connect it so you can see the meter when driving. Then if the voltage goes away when the car acts up, you know it is an ignition problem. Once you know for sure if it is a fuel or ignition problem, than you know where to spend your diagnostic time and what parts need to be tested. Some of the ignition parts, like the coil packs and modules can be tested off of the car with the proper equipment. But when you get one that only acts up sometimes, it can be a lot more difficult to find the problem. Sometimes something as silly as a loose ground wire or bad connection in the system, can drive you nuts trying to find it. Have them give some of these things a try and see if it doesn't help isolate the problem. You could also buy a spray can of starting fluid and a screw driver, to keep it in the car and the next time it acts up just spray a shot of the starting fluid into the intake and see if that makes it start right up. If so, that would be a pretty good indication of a fuel delivery problem. If it makes no change, then suspect ignition problems. The big trick to fixing it, is going to be to get it to act up when it can be tested. Thanks

Bob, Auto Service Technician
Category: Car
Satisfied Customers: 4087
Experience: 40 year GM Tech. +30 Certified. ASE Master Tech.(expired, retired) Medium Duty, Heavy Line, Retired
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