1981-1983 Imperial EFI Hot-Start Problem Diagnostics

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Hot Start Problem:

Chrysler TSB 14-30-83 for all EFI Imperials talks about Hot Start problems. This usually occurs 10 to 15 minutes after shutdown, requires excessive cranking, rough running for 30 seconds and is much worse in warm climates. The ohmmeter test is correct, the Pressure Switch must read no more than 10 ohms between the tip of the switch and the Tee in the piping. It then says to replace the pressure switch with part no. 4091901, which has not been available for years. Also a dealer training session listed "excessive resistance" in the pressure switch as a cause of the problem. I think that heat soak is the larger part of the problem and that this heat literally boils the gas out of the injection system much like a carbureted system also reacts to heat.


Diagnosis and Repair:

If the resistance test is okay, try the method of putting the throttle almost wide open while cranking - this will not only tend to clear the rich mix in the manifold, but will also prevent additional fuel pumping and you should get a better start.

The Air Cleaner Cover must have a gasket under the lid, I think I talked about this last week. I have never run with the clamping band, but am sure the gasket is still soft, turning it upside - down can return some resilience, best to replace. There is no seal at the wing nut.

The oozing is from the melting of the original potting compound used in the Power Module and the Fuel Metering Module. It has caused many cars to idle poorly since it kept the throttles open, not allowing the Throttle Switch to close and returning the engine to normal fuel mix and spark timing.

If it is flooding, I think that the nozzle assembly may be weeping fuel into the intake after shutdown. This could be due to seepage at the fuel line connections inside the unit, or it could be due to poor condition o-rings inside the fuel valves (part of the nozzle assembly). If you want to just investigate those o-rings and the fuel line connections, it is easy to get the assembly out and apart, and it is pretty foolproof to reassemble. You will have to find o-rings of the proper size (easy) that are qualified to operate in modern fuels (probably need to ask about this).

A way to see if this seepage is happening would be to run the car with the air cleaner lid off. To do this, you have to fool the computer into thinking that you are cranking to start (so it will ignore the airflow sensor). You do this by providing 12 volts to the #18 tan wire which you remove from the starter control relay connector. This wire is labeled "S5 18TN". This is a tricky operation, because the system will provide fuel for as long as this wire is energized, and you'll have a really flooded engine unless you do things in the right order: You need to have someone else start the car in the normal fashion (or else you start it from under the hood by leaving the key on, then touching the starter control wire "S5 12BR" to the battery + post to crank the engine) while simultaneously, putting the tan wire on the + post, this will keep it running with the cover off the air cleaner indefinitely.

Now you are in a position to observe the fuel nozzles doing their thing (don't get your eyebrows singed!) and you should be able to see any seepage around the connections. If the seepage is occurring inside the nozzle assembly, though, you will have to detect it by shutting the engine down and then observing if any fuel seeps out the nozzles, perhaps by putting a paper towel under them. This by the way is a pretty common thing, I have had a couple of these cars do this to me, and it is damn hard to find, since normally there is no way to watch while the car is running.

I guess one thing I would do before throwing money at the problem is to take a small quantity of gas with you (you only need a few ounces) and when you have produced the condition you think will cause the symptom, before you do try to start the car, open the hood, momentarily loosen the wingnut in the center of the air cleaner, and pour about 1 1/2 oz of gas into the center depressed part of the lid, this will quickly rundown the screw threads and into the intake manifold. Now quickly tighten the wingnut, and try to start the car. If it now starts every time and quickly, we have isolated the problem to delay of fuel-delivery. Now we have to figure out why.

Next step, assuming this is the problem, is to run a wire out of the HSA area (you can snake it through the air inlet so you do not have to violate the tight air seal) and connect it to the hot side of the control fuel pump connector, which has only two wires. ( I think you want the light green wire, but I'm color blind, so make sure the other wire [black?]is ground, then the light green wire is the one you want) .

Outside, connect the wire to a test light so you can see when the pump is being told to run. This light should light brightly every time you cycle the key to off, then back to on-crank. Only very briefly, mind you, if the car has just been running, but it should at least flash bright, showing the purge cycle is happening.

If it is, and no gas is being delivered, I think you have a fuel leakage or vaporization problem in the nozzle or tubing area inside the HSA.

If the light is not coming on, there is an electronic problem, but there are a couple of possible locations. One is our old friend the ASDM.

The ASDM can be eliminated as a culprit by bypassing it totally. Take a short length of #12 wire and connect the two LARGE wires (one blue, the other, green, both #12) in the 5-socket connector that you disconnect from the ASDM. If the problem persists, the FPS is still suspect, along with the power module.

This page was last updated on August 26, 2001.  Send us your feedback, and come join the Imperial Mailing List - Online Car Club