Tech Area

Stumbles Then Shuts Off

Question: I need your advise on my problem. If I could take a few moments out of your busy day, I will appreciate it.

My '86 2.8L developed a stalling or stumbling and then died just as I drove it into my garage after a 30 mile trip on the interstate. The next day (25 F) it started normally, but then stumbled and died after about 1 minute. I had a code 15 from a few days ago and thought it was the coolant sensor causing the problem, so I replaced the coolant sensor. I also reset the ignition timing to 10. Engine starts, idles, stumbles, dies after 1 minute - no change.

I checked the EGR valve for stuck open condition, it wasn't open. It is a new EGR valve. I replaced the ignition module and the pickup coil since they were about 20,000 miles old. Engine starts, idles, stumbles, dies after 1 minute - no change. As the engine stumbles and dies, the oil pressure gage is still reading about 60 psi. The Helms '86 service manual says I have says to check the fuel system.

When I turn the ignition key to on (run, not crank) the fuel pump is supposed to run for 2 seconds. I don't hear it running when I do this. All of the fuses are ok. The manual says to check the injectors, fuel pump relay, fuel pressure, and oil pressure sensor. I don't have a tester for the injectors (null light?). Can I check the injectors with something else? How can I check the oil pressure sensor? I might be able to fabricate a fuel pressure tester. Any suggestions?

Of course this is my daily driver, even in Wisconsin winters, and I'm running out of favors asking for a ride to my job.

Answer: You can do a "laymans" check of the fuel pressure by the following. Remove the cap from the schrader valve on the fuel rail. It is just before the fuel rails disappear under the upper pleneum, right behind the thermostat housing. Takes a finger from each hand as there is not enough room for a thumb and finger. Sorta looks like a large tire valve cap.

When it is removed, cycle the key 5 sec on, 10 off, about 4-5 times. You have to lean directly over the valve (looks like a tire air valve) to see it. Position a key or something to depress the schrader valve and then move your head away and press it down. A high pressure squirt of fuel should hit the bottom of the decklid (the reason for moving your head). 6-12" should run the car, but anything else will not.

Replace the fuel filter and recheck. If still no pressure, then plan on replacing the fuel pump. Even if ECM or relay will not turn the pump on, the oil pressure sender will as soon as 4 lbs pressure is achieved, and it will stay on to run the car. You should also check (immediately after the engine shuts off) to see if you have ignition spark. Removing the coil wire at the coil and turning the engine over should produce a spark from the coil tower to the metal magnet of the coil. If not, then something in the ignition is bad. Pick-up coil, module, module to coil pigtail, or coil.

New parts can be faulty. You need to ascertain if you have spark and fuel pressure. This does not sound like a faulty sensor.

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