97 Astro intermittent start problem
4ntzilla
07-17-2010, 12:30 PM
Intermittent start problem. The longer the van sits the longer it takes to start.Starts first try with starter fluid. Runs fine, just hard to start. Fuel pressure 58-59psi with key in on position. Fuel pressure drops 10psi within 3 min. Hooked fuel pressure gauge in right before fuel filter(rigged up with a section of hose and some clamps) and fuel pressure still leaks down 10psi within 3 minutes. I wanted to be sure that something under the upper intake was not causing my leak down issue. I now feel 90% certain that its the fuel pump. If anyone has any other ideas please let me know. Thanks
Blue Bowtie
07-18-2010, 11:59 AM
Welcome Aboard!
It's good that you tested before the filter. Although a clean filter is always a good idea, your test all but rules out a filter being the main problem.
The rate of leakage shouldn't be preventing the pump from making and maintaining pressure. If the pressure dropped immediately after the pump shut down I would be more concerned over the leakage rate.
Fuel pumps are extremely sensitive to voltage. You need to verify that the pump has 12.6V at the pump, not just in the pump circuit of the wiring harness. There are several connectors between the pump relay and pump itself. The most suspect connector is right at the fuel tank pickup unit. They tend to heat and fail, causing undervoltage and the resultant low pressure.
http://www.wwdsltd.com/files/PumpConnector.jpg
It's good that you tested before the filter. Although a clean filter is always a good idea, your test all but rules out a filter being the main problem.
The rate of leakage shouldn't be preventing the pump from making and maintaining pressure. If the pressure dropped immediately after the pump shut down I would be more concerned over the leakage rate.
Fuel pumps are extremely sensitive to voltage. You need to verify that the pump has 12.6V at the pump, not just in the pump circuit of the wiring harness. There are several connectors between the pump relay and pump itself. The most suspect connector is right at the fuel tank pickup unit. They tend to heat and fail, causing undervoltage and the resultant low pressure.
http://www.wwdsltd.com/files/PumpConnector.jpg
drew300
07-19-2010, 11:52 AM
I too had your type of problem on my '97.
When I phoned GM Service, they said "60 psi minimum". I had 59 psi.
I measured the current draw of the pump by placing an ampmeter in the circuit by removing the pump relay and putting the meter probes in there ( I can't remember which pins, but it was marked on the relay cover) (and be careful, you don't want to think about using the wrong pins). My old pump drew 4.5 amp. The new draws 10. It works fine. My new after-market pump came with a warning to check for bad connectors, and supplied a grease to put on the connectors, to limit corrosion. Also, there is a black ground wire from the tank upper area to chassis ground, at the front area of the tank. Make sure this is clean as it's the pumps' ground wire. Mine was corroded, so i cleaned and greased it. Good Luck
When I phoned GM Service, they said "60 psi minimum". I had 59 psi.
I measured the current draw of the pump by placing an ampmeter in the circuit by removing the pump relay and putting the meter probes in there ( I can't remember which pins, but it was marked on the relay cover) (and be careful, you don't want to think about using the wrong pins). My old pump drew 4.5 amp. The new draws 10. It works fine. My new after-market pump came with a warning to check for bad connectors, and supplied a grease to put on the connectors, to limit corrosion. Also, there is a black ground wire from the tank upper area to chassis ground, at the front area of the tank. Make sure this is clean as it's the pumps' ground wire. Mine was corroded, so i cleaned and greased it. Good Luck
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