“when hot; cranks but wont start problem”
03-17-2005, 09:18 AM
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“when hot; cranks but wont start problem”
This is the “when hot; cranks but wont start problem” again-’79 911 SC-the engine takes a little while to start when cold (10 to 15 attempts)-starts perfectly when warm, but is impossible to start when hot and I have to wait 3 to 4 hours for it to cool down….
I changed the check valve and tested the accumulator which seems to be OK. After several weeks of trying various things I relented and took the car to the only Bosh technician in Zimbabwe. He is pretty good and has more than a working knowledge of the Porsche K-Jetronic system.
The fuel pressures are all over the place, which I am told points to a problem with the Warm up Regulator. The Fuel Distributor was taken off and cleaned and it appears that the previous owner may have worked on it as there are spanner and screwdriver marks on it. I am told that this is not a good sign as this is not a very easy part to service even by extremely well trained professionals with all the best kit. So I may be looking at a new fuel distributor.
The injectors are OK, not as good as new, but certainly no where near bad enough to cause the problems that I am having. I have always wanted to keep the car as original as possible, but my problem now is that replacing the WUR the fuel distributor and some pipes are going to cost a lot of money and I am wondering if it might not be wiser to fit an aftermarket multipoint fuel injection system. I know very little about them, but they should be more reliable than the K-Jetronic system and may very well be cheaper and might even give me more power. I am also considering fitting carbs to the car. All advice greatly appreciated.
Russell
Zimbabwe
I changed the check valve and tested the accumulator which seems to be OK. After several weeks of trying various things I relented and took the car to the only Bosh technician in Zimbabwe. He is pretty good and has more than a working knowledge of the Porsche K-Jetronic system.
The fuel pressures are all over the place, which I am told points to a problem with the Warm up Regulator. The Fuel Distributor was taken off and cleaned and it appears that the previous owner may have worked on it as there are spanner and screwdriver marks on it. I am told that this is not a good sign as this is not a very easy part to service even by extremely well trained professionals with all the best kit. So I may be looking at a new fuel distributor.
The injectors are OK, not as good as new, but certainly no where near bad enough to cause the problems that I am having. I have always wanted to keep the car as original as possible, but my problem now is that replacing the WUR the fuel distributor and some pipes are going to cost a lot of money and I am wondering if it might not be wiser to fit an aftermarket multipoint fuel injection system. I know very little about them, but they should be more reliable than the K-Jetronic system and may very well be cheaper and might even give me more power. I am also considering fitting carbs to the car. All advice greatly appreciated.
Russell
Zimbabwe
03-17-2005, 12:39 PM
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if you can get this book http://www.amazon.com/exec/obidos/AS...278169-9880909
I think you could turn into the second bosche technician in Zimbabwe
I think you could turn into the second bosche technician in Zimbabwe
03-17-2005, 02:10 PM
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As I recall, there really are no serviceable components in the fuel distributor. The plunger in it is mated to the particular fuel distributor. If thinking about Carbs, read Bruce Anderson's Porsche 911 Performance Handbook. If I still had my 81SC and didn't have to worry about emissions, I'd change out the fuel injection for carbs and probably upgrade to the Max Moritz-style 3.2L cylinders and pistons in a flash.
03-18-2005, 05:30 AM
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The Porsche CIS injection is very reliable and virtually maintenance free.
The key, though, for good starting is a properly setup & functioning WUR.
The control pressures (cool & hot) need to checked (1.0 to 1.5 bar cold
10 deg C & 2.8 to 3.5 @ 40 deg C). I would never consider changing to
carbs unless you're racing or you like to use a lot of fuel.
By-the-way, why have you assumed the problem to be fuel related?
You must have checked for a good spark when hot, right?
The key, though, for good starting is a properly setup & functioning WUR.
The control pressures (cool & hot) need to checked (1.0 to 1.5 bar cold
10 deg C & 2.8 to 3.5 @ 40 deg C). I would never consider changing to
carbs unless you're racing or you like to use a lot of fuel.
By-the-way, why have you assumed the problem to be fuel related?
You must have checked for a good spark when hot, right?
03-18-2005, 09:02 AM
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I have checked for a good spark, much the same cold and hot. The fuel pressures are all over the place so it does look like the WUR, I will most probably replace that first and then the fuel distributor if that has not sorted it. I am glad to hear you say that the Bosh system is good as I want to keep the car orginal, but if there are significant improvements to be had from an aftermarket mulitppoint injection system I may consider them.
03-18-2005, 01:15 PM
#6
"I will most probably replace that first and then the fuel distributor if that has not sorted it."
Be very sure about replacing the fuel distributor as they are very reliable and rarely
if ever fail,
unless damaged by water contamination or someone's improper servicing. They are very costly new or rebuilt.
Be very sure about replacing the fuel distributor as they are very reliable and rarely
if ever fail,
unless damaged by water contamination or someone's improper servicing. They are very costly new or rebuilt.
03-31-2005, 12:57 AM
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Your injectors need to spray a misty like pattern.it is a problem if they arent. dont replace the dist cause someone made a scare on it,its in side that counts. do the war,adjust the pressures,test the thermo switch(12v under cranking,wait about 10 seconds and the volts will drop) co mixtures adjust with a machine. from there you have somewhere to start.... good luck. oh also, be patient,all trouble shooting takes time,hot to cold.....
