SC won't fire on number 1
Discussion
I have been experiencing probs over the last few weeks with a slight misfire on number 1 cylinder and more recently a warm start problem.
On Friday things took a turn for the worse - the car wouldn't properly and my oil level started to rise (fuel I am assuming).
Well - after carrying out various tests I have come to the conclusion that might slight miss on number 1 cylinder has got much worse. In fact it is not firing at all!
The question is why.
I have changed the fuel injector, the plug, the distributor cap and rotor arm. I have swapped leads.
When I put a spare plug on the offending lead I get a regular strong spark.
I have done a quick compression test and am getting well over 100 psi on 1 and 2, and that was with the remaining plugs still in place and a cold engine! I am assuming that if there is something seriously mechanical wrong in the cylinder my compression would be much less - and the cylinder would still fire slightly at idle.
The plug in 1 is always soaked with fuel and stone cold when I pull it - and my oil level is still rising!!
The only other thing I can thing to check is the valve clearances. So that's the next (and last) thing on my list.
Help!!!!!
Danny
On Friday things took a turn for the worse - the car wouldn't properly and my oil level started to rise (fuel I am assuming).
Well - after carrying out various tests I have come to the conclusion that might slight miss on number 1 cylinder has got much worse. In fact it is not firing at all!
The question is why.
I have changed the fuel injector, the plug, the distributor cap and rotor arm. I have swapped leads.
When I put a spare plug on the offending lead I get a regular strong spark.
I have done a quick compression test and am getting well over 100 psi on 1 and 2, and that was with the remaining plugs still in place and a cold engine! I am assuming that if there is something seriously mechanical wrong in the cylinder my compression would be much less - and the cylinder would still fire slightly at idle.
The plug in 1 is always soaked with fuel and stone cold when I pull it - and my oil level is still rising!!
The only other thing I can thing to check is the valve clearances. So that's the next (and last) thing on my list.
Help!!!!!
Danny
A similar thing happened to the Hart engine in my single seater. In the end it turned out to be a management problem where for some bizarre reason it was sending far too much fuel to one injector. Naturally with so much fuel swilling about it was simply drowning the plug, so down the bore it went. Apart from a slight misfire originally it was difficult to really determine the problem. The drysump tank overflowing with a mixture of fuel and oil was disconcerting, but did give the game away. Fuel is not a very good lubricant, so a total rebuild is now happening. If your valve clearances turn out to be OK, and realistically they would have to be well out to suddenly stop the cylinder from firing, I reckon a look at fuel delivery quantity might be worthwhile. It may be worth trying to start the car with the choke system disabled in case the problem is on this side, as by the time the choke is cutting out the plug could be so wet it will not recover. There are instances where due to the lead or plug, the plug will not spark under compression but seems OK when out of the engine. Is 100 psi a decent figure for a compression test on a 911? At a guess it does not seem all that great to me, although allowance has to be made for the lack of lubrication and therefore sealing on No1. I would suggest you speak to a Porsche specialist. Sometimes the oddest problem is something they have seen before and they can go straight to it, whereas you or I could spend days on the process of elimination. Good Luck.
On and I forgot to mention that I had tried swapping the fuel injector pipes with number 2 cylinder and it still had the same problem.
The compression was just under 150 psi on one spin and I didn't want to go mad as I had the other plugs still in - I was just making sure I had some compression!
The compression was just under 150 psi on one spin and I didn't want to go mad as I had the other plugs still in - I was just making sure I had some compression!
Hi there
Not sure if the SC has the Beru connecters, (mine does)
There are two types, one type that should measure 2.9K ohms and the others sould measure 4K ohms, whichever type you have they should all measure within 200 ohms.
They also tend to breakdown under load.
Worth checking, otherwise it could be really bad valve
guide.
Try www.pelicanparts.com, go 911 bul board, you have to join to post, but it's free, there are plenty of SC people there.
jeff
edit valve guide - forgot test of cyl - sorry
>> Edited by jeff m on Monday 16th December 00:49
Not sure if the SC has the Beru connecters, (mine does)
There are two types, one type that should measure 2.9K ohms and the others sould measure 4K ohms, whichever type you have they should all measure within 200 ohms.
They also tend to breakdown under load.
Worth checking, otherwise it could be really bad valve
guide.
Try www.pelicanparts.com, go 911 bul board, you have to join to post, but it's free, there are plenty of SC people there.
jeff
edit valve guide - forgot test of cyl - sorry
>> Edited by jeff m on Monday 16th December 00:49
Colin,
I haven't got access to a leak down tester but am planning on connecting the compressor up and seeing if I could hear anything in the exhaust/inlet.
Have you ever heard of a fuel distributor going faulty on one outlet only and flooding the plug? I am going to swap the fuel pipes round and see if the problem moves to another cylinder - but it seems pretty unlikely to me.
Do you know where I could buy a CIS pressure gauge?
Thanks
Danny
I haven't got access to a leak down tester but am planning on connecting the compressor up and seeing if I could hear anything in the exhaust/inlet.
Have you ever heard of a fuel distributor going faulty on one outlet only and flooding the plug? I am going to swap the fuel pipes round and see if the problem moves to another cylinder - but it seems pretty unlikely to me.
Do you know where I could buy a CIS pressure gauge?
Thanks
Danny
No, but I do know where you can find a good specialist with leakdown and K-Jet test equipment....
Danny, bite the bullet and get it professionally looked at, the SC is a reliable old girl so you do not need to buy the stuff yourself (the K-jet test kit was £470, the leak down unit around £120) when for a hours or so labour (around £80) you will know all there is to know. Sometimes although your skill levels are not in question, it is better to get help.
Oh, and yes, I have known a metering head go down on one cyl, swap the pipes and see if it transfers to another cylinder.
Danny, bite the bullet and get it professionally looked at, the SC is a reliable old girl so you do not need to buy the stuff yourself (the K-jet test kit was £470, the leak down unit around £120) when for a hours or so labour (around £80) you will know all there is to know. Sometimes although your skill levels are not in question, it is better to get help.
Oh, and yes, I have known a metering head go down on one cyl, swap the pipes and see if it transfers to another cylinder.
Danny
I assume you have run the car in the dark to check for arcing of HT leads.
Check vacuum to distributer for leaks.
Also try tapping the injecter with engine running.
Failing that pull the injecter and get it checked for openning at too lower pressure.
(If it opens at too low a pressure then it would be constantly dripping) I know it's relativly new but...
If not then you may have to remove the valve covers to check the valves. If one of the valves has a large gap there could be a small peice of crap stopping the valve seating. You will also be able to check for play in the guides.
I assume you have run the car in the dark to check for arcing of HT leads.
Check vacuum to distributer for leaks.
Also try tapping the injecter with engine running.
Failing that pull the injecter and get it checked for openning at too lower pressure.
(If it opens at too low a pressure then it would be constantly dripping) I know it's relativly new but...
If not then you may have to remove the valve covers to check the valves. If one of the valves has a large gap there could be a small peice of crap stopping the valve seating. You will also be able to check for play in the guides.
www.pelicanparts.com/techarticles/bob_tindel/911_inj_nozzle.htm
Danny read the above link it may help.
Jeff
Danny read the above link it may help.
Jeff
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