Solved the 280GE backfiring with new HT leads. but now will not start after engine has reached working temp. If I stop to fill up with fuel etc she will not start until engine is cold. I can smell fuel as if its flooded when trying to start when warm. Any ideas???
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Sounds like it may be stuck on if you have one - that would flood the engine when hot.
Does it fire at all ?
Usually new problems that appear after you've been 'in there' are usually down to something you've disturbed, but I guess you've had a really good look round already for that kind of thing.
CSI system is a good place to start. Either injector leaking, or temp switch failed closed. Use teh VOM to see if there's power at the CSI when warm (shouldn't be). If there isn't, then pull the injector and test for leak as in the article on CGW G-tech.
Does the car otherwise run properly, with fast idle when cold, slowing to 800 rpm when warm?
Ian,
You say it was backfiring, plus I seem to remember from one of your other posts it has an LPG conversion.
If thats the case does the conversion include a plunger type device that fully opens the CIS air flow flap when running on LPG? This is designed to protect the CIS system if backfires occur when running on LPG.
If not the backfires (associated with the dodgy leads and running on LPG I presume) may have damaged and or caused some mis alignment of the air flow flap.
Yes the first time it backfired the airflow flap did bend. I have replaced it, but it was still running rough so I tweaked timing to see if it made any difference. It wasnt until I realised the leads were of inferior quality and creating a firework display in engine bay that I put old ones back on. Since then runs sweat but subsiquently the idle when warm is now 1100 rpm so I need to drop idle to 850. I haven't done this yet and I now wonder if when I turn engine off that the idle is to high it runs on a bit longer than normal and allows fuel in when finally stops. Cold start injector has been doing what is should be, running fast when cold and cutting out when warm but as I said idle RPM is about 1100 so I will drop to 850 and see if that makes any difference.
Another point is when I do switch off when warm and try to start again will fire for 1-2 sec then die and just will not fire after that but can smell fuel when trying.
Cold start injector has been doing what is should be, running fast when cold and cutting out when warm but as I said idle RPM is about 1100 so I will drop to 850 and see if that makes any difference.
That's the warmup compensator doing its job. The cold start valve is only a short term shot of fuel to start at low temperature. The warmup compensator varies the fuel pressure at the fuel distributor during startup; and this causes the high idel rpm ffollowed by a slow down as the engine warms.
Don't forget the air component that goes with that WUC fuel
While the WUC on the fuel inlet line is regulating pressure down to richen the mixture, there is also another valve that's open to let additional air bypass the idle speed control screw. It's a rotary valve where the disk is rotated by a bimetalic spring to expose a hole letting extra air in when it's cold, and close off when it's warm. It's a bugger to locate and worse to work on. It's under the intake manifold (follow the 5/8 hoses routing under there to find it). Maybe your high idle is due to some part of THAT system being damaged by a backfire. If it was harsh enough to bend the air meter plate, no telling what other weak link may have failed.
Given that it starts OK from cold this does suggest that the cold start injector is working.
High idle could indicate problem with warm up regulator as per Dave and Dutch.
However not starting at all when hot could suggest, especially given recent damage / parts replacement, that it is running way too weak. It would still smell of petrol but the mixture will not ignite.
Does it run on when you switch off?
Can you force it to start on LPG? If yes that would exclude the WUR.
Suggest getting a gas analyser on it.
It's the only real way to set it up properly. The mixture needs to be set in concert with the idle speed, all this done with a warm engine, and then let the chips fall where they may when the CSI, WUC, etc do their things to start and run cold.
There's a little write up on the use of the gunson gastester in the G-tech article on setting the 280's idle. Also a bit in the "specials" section of CGW where the tester is offered for sale. You may have a better source local in the UK though.
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