debugging my CIS-hot start issue
09-22-2005, 10:45 AM
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debugging my CIS-hot start issue
How do I tell if my fuel pump has an integral check valve?
I have a '78 engine in a '75 body and am not sure if I have the correct mix of parts. The car will not start when hot. Pump, accumulator, filter, fuel dist are all new or rebuilt. WUR is of unkown origin.
I also have a few other classic problems, unstable hot idle and low speed bucking, but one thing at a time.
Thanks
I have a '78 engine in a '75 body and am not sure if I have the correct mix of parts. The car will not start when hot. Pump, accumulator, filter, fuel dist are all new or rebuilt. WUR is of unkown origin.
I also have a few other classic problems, unstable hot idle and low speed bucking, but one thing at a time.
Thanks
09-22-2005, 02:42 PM
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CO is unknown, plugs are bosch platinum, not sure of #. This is an engine that has been sitting for a long time and is just being brought back to life, so not much history with it for me.
Starts well cold and runs well under power, but has hot idle and hot start issues. Still need to track down possible vac leaks. The check valve was something I thought I could check for pretty easily.
Starts well cold and runs well under power, but has hot idle and hot start issues. Still need to track down possible vac leaks. The check valve was something I thought I could check for pretty easily.
09-22-2005, 02:59 PM
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Just went through diagnosing hot-start issues on my 930 that surfaced (oddly enough) after I began not driving it for long periods of time and leaving it in the garage. Basically mine would run fine when hot, but it either would not start, or required an inordinate amount of cranking to get it going, if it would go at all.
1. rule out vacuum leaks and/or spark issues;
2. Get the CIS pressure gauges;
3. Check the Warm Control pressure at the WUR - it varies by year/model, but generally your warm pressure should be around 3-5 bar;
4. Check for residual pressure in the system 15 minutes after shut-off (I think it should maintain at least 1 bar pressure after 20 mins - not sure on the exact figure, since I don't have access to my documentation right now);
5. If all of this uncovers nothing, believe it or not, it could be as simple as leaking injectors that are bleeding off pressure between the fuel distributor and injectors and in effect, causing localized vapor lock in the injector lines. You can test this by removing the injectors while the engine is hot and looking for any drips (there should be none). As it turned out, this was my problem - I put a couple of bottles of techron concentrate in the tank, took it for a couple of nice long drives and everything came back into spec. YMMV - good-luck.......
- John
1. rule out vacuum leaks and/or spark issues;
2. Get the CIS pressure gauges;
3. Check the Warm Control pressure at the WUR - it varies by year/model, but generally your warm pressure should be around 3-5 bar;
4. Check for residual pressure in the system 15 minutes after shut-off (I think it should maintain at least 1 bar pressure after 20 mins - not sure on the exact figure, since I don't have access to my documentation right now);
5. If all of this uncovers nothing, believe it or not, it could be as simple as leaking injectors that are bleeding off pressure between the fuel distributor and injectors and in effect, causing localized vapor lock in the injector lines. You can test this by removing the injectors while the engine is hot and looking for any drips (there should be none). As it turned out, this was my problem - I put a couple of bottles of techron concentrate in the tank, took it for a couple of nice long drives and everything came back into spec. YMMV - good-luck.......
- John
09-22-2005, 03:06 PM
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art,
Right now I'm struggling with an 82 SC and found out the CIS injectors are clogged.
The car was sitting down for a couple of years. It had cold start problems, but once fived the head temp sensor the propblem was fixed. Now it has a bad hot idle once the cold start injector stops. This is due to the dirty injectors since thy dont have enough pressure to make a decent spray, but once it is at WOT after 3500, it cleans pretty nicely (I guess more fuel pressure) but still needs some fuel.
Does this make sense Peter?
Right now I'm struggling with an 82 SC and found out the CIS injectors are clogged.
The car was sitting down for a couple of years. It had cold start problems, but once fived the head temp sensor the propblem was fixed. Now it has a bad hot idle once the cold start injector stops. This is due to the dirty injectors since thy dont have enough pressure to make a decent spray, but once it is at WOT after 3500, it cleans pretty nicely (I guess more fuel pressure) but still needs some fuel.
Does this make sense Peter?
