1996 ASTRO will not start

My 1996 Astro with 140,000 mile stalled a week ago and will not start. It showed no signs of a problem, it just quit. I was able to read the an error code from the ECM and it say P300, random missfire. I checked for spark by pulling a plug and seeing I had a spark when you turn the engine over. Then I connected a fuel pressure guage and noted I had 50 psi but it drops off alsmost as soon as I would stop turning the engine over. Chevy suggested I had a bad fuel pressure regulator so I changed it, but it still will not start. I connect a scope to the mass air flow sensor and can see it is sending a signal. I have run out of ideas as to the cause. I would welcome some new ideas on the problem.

Thanks.

There are several choices here. The first requires compression, which you can sometimes hear when cranking. The sudden death raises questions. I suspect ignition; you might try spraying carb cleaner or starting fluid carefully down the intake. Be careful hereas this stuff is HIGHLY flammable. If the engine starts, the problem is likely fuel related, however, this stuff will actually ignite with compression, if it exists. Try that and get back to me. Ray

Great suggestion. I sprayed a few squirts of Carb cleaner (injector safe type), into the intake and it started up until the fuel was gone, about 10 seconds. Long enough to hear that everything seemed normal. This makes me confident I do have a fuel problem. The fact that I cannot hold a pressure in the fuel line makes me think I might have a small leak in the fuel line. I am going to investagate the fuel hoses tomorrow. I plan to remove the fuel line from the fuel filter and connect the pressure guage to block the gas complety. When I turn on the key the fuel pump should build pressure and it should have not place to bleed off. If it does, I will look for the problem in the fuel line to the tank or the pump assembly its self. If it holds, then I am still looking for why the Fuel injector body it allowing the pressure to bleed off. Any more suggesting are welcome.

George

Great suggestion. I sprayed a few squirts of Carb cleaner (injector safe type), into the intake and it started up until the fuel was gone, about 10 seconds. Long enough to hear that everything seemed normal. This makes me confident I do have a fuel problem. The fact that I cannot hold a pressure in the fuel line makes me think I might have a small leak in the fuel line. I am going to investagate the fuel hoses tomorrow. I plan to remove the fuel line from the fuel filter and connect the pressure guage to block the gas complety. When I turn on the key the fuel pump should build pressure and it should have not place to bleed off. If it does, I will look for the problem in the fuel line to the tank or the pump assembly its self. If it holds, then I am still looking for why the Fuel injector body it allowing the pressure to bleed off. Any more suggestiions are welcome.

George

Another thing you might check. Under the battery tray there are wires that sometimes get corroded from acid and could break.

1996 ASTRO now starts. Thanks for the help. I was able to find the problem and repair it. The problem was traced to loss of pressure in the fuel line. I attached a fuel pressure gauge to the test port on the fuel line near the rear of the engine, on the driver side. When you turned the key on the fuel pump runs and you can see about 40 psi. As soon as the pump stops the pressure drops to 0 psi. I had assumed the problem would be the fuel pressure regulator in the upper intake manifold, and replace it without success. After thinking about the problem the only other place pressure could be lost would be the fuel line, or something in the fuel tank. If it were a leak in the line you probably would smell gas and notice a place where it was spraying. I did a visual inspection of the fuel lines (hoses) and did not find any indication of a gas leak. To test if the problem was in the tank or engine, I pulled the hoses out of the throttle body by disconnect them at both ends. The fuel and fuel return steel hoses are connected together and are around 12 inches long. The hose that carries fuel to the engine has the pressure monitor valve in it. With the hoses removed I plugged the end of the hose that carries fuel to the engine using a short piece of rubber fuel hose, with a bolt that fit tightly in one end and used a hose clamp to hold it to the steel fuel hose and another clamp to hold the bolt on. The fuel line is under pressure and probably would push the blockage (the bolt) out if you did not clamp it on. It was a bit tricky, but I then connected the steel hose with the pressure monitor connection in it back to where I disconnected it from on the van. Now when I turn the key on and if the pressure holds the problem is still in the engine. If the pressure still bleeds off then the problem is before the engine. I turned on the key and sure enough, when the pump stopped the pressure bleed off. My problem was before the engine. Since I did not see any leakage around the hoses I was pretty sure the problem had to be in the fuel tank. I dropped the tank. Dropping the tank required disconnecting about 4 hoses before it can be lowered. So when you get it out the only umbilical to the van are the wires to the fuel level sender and fuel pump. I was able to slide the tank out form under the van and get good access to the hoses coming out of the tank. Using the “T” that came with the fuel pressure gauge I connected the pressure gauge to the center “T” connection. Then to block the through port I again used rubber hose and a bolt to block the end where fuel would spew out. Another short rubber hose connect the last opening of the “T” to the fuel hose coming out of the tank. Hose clamps were used to hold all the connections. Since the wiring was still attached I was able to turn the key on. The fuel pump started running; pressure was building and peaked at about 60 psi. The pump stopped running and I could hear the pressure bleeding off inside the tank. I disconnected my measuring lash up and removed the float and fuel pump from inside the tank. Inspection of the assemble showed the pulsar had a bad rubber gasket. I do not know what a pulsar does, but it is a small body that looks like a miniature master cylinder. It connects the fuel pump output to the hose that leaves the fuel tank. Each end of the pulsar has an opening and the stem of the fuel pump pushes in one side and the steel hose of the fuel line pushes in the other. Rubber gaskets seal the connections. I clearly had a mangled gasket on the pump end. I replaced the pulsar and installed the pump and float back into the tank. I again connected my pressure test setup and turned on the key. Pressure built to 60 psi, the pump stopped, and the pressure held. It was time to put it all back together. Once everything was reassembled, I connected the pressure gauge to the test port at the back of the engine, and turned on the key. The pressure built up to about 50 psi, the pump stopped, and the pressure held. I continued turning the key and started the van. It ran fine. In all, testing, removing the fuel tank and replacing the bad pulsar took about 5 hours. Chasing the wrong problem added over week.

Troubleshooting will not start- reviewed

1. Van dies; engine turns over but will not start
2. Pulled a spark plug, turn engine over observe spark (probably not a electrical problem)
3. Squirt a small amount of intake cleaner into the intake, start engine, runs briefly (fuel problem)
4. Connect a fuel pressure gauge, turn key on, fuel pump starts, pressure builds, pump stops, pressure bleeds off. (problem either at the engine or fuel tank, or a hose)
5. Inspect fuel hoses for sign of leaks. (none found)
6. Remove fuel hose from engine, plug the end. With fuel pressure gauge attached, turn key on, pressure builds, pump stops, pressure bleeds off. (problem not in engine, probably in fuel tank)
7. Remove fuel tank, attach pressure gauge, turn key, 60 psi while pump is running, pump stops, pressure bleeds off. Hear pressure escaping inside tank. (problem in tank)
8. Remove pump and sender from tank, inspect and see gasket on pulser bad. (found problem)
9. With new pulsar install and tank put back together, test for pressure again. (pressure held after pump stopped, just like it should)
10. Put it all back together. (job successful)

The problem was identifying if it was a fuel, or electrical problem. Once I knew it was fuel I had to devise how to test for where the problem was. I hope it help others find there problems. I really appreciated the suggestion of squirting a bit of intake cleaner in the intake. That put me on the right track.

Thanks,