SC won't fire on number 1 - Page 2 - Porsche General - PistonHeads UK

Danny, see if this site helps p-car.com

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.

The injection system (CIS)is mechanical and all injectors pump fuel continously. Therefore I cannot see a way that there would be more fuel going to one injector only - although the thought had crossed my mind.

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!

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

Try swapping injecter. # 1 could be squirting instead of spraying and not atomising fuel jeff (I'm trying to think of the cheap cures first)

I have tried a different injector (I replaced them all about 6 months ago), but what is a Beru injector? Are you thinking of the 3.2 which has electronic fuel injection? My car is a 3.0 SC with mechanical injection Danny

Please read my post on your check valve posting.

I do feel resistance on the flap, cheers for the idea Laurence Danny

It seems we have the same taste in cars (wedge and 911) The Buru connecters are the brown connecters between plug and lead. As I said, not sure if your car has them as mine is a MFI car. But they are difficult to test (definitively) and can cause some ilogical faults. Jeff

Cheers Jeff, My SC has black connectors between the leads and plugs, but I have swapped the leads and it still doesn't fire on 1 Danny

Danny, A perfect SC will compression test at 175-200psi. Do a compressed air leak down test as well and listen in the exhaust pipe, air box and oil tank. Also check for a loose valve clearance. I suspect that you have bent a valve.

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

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.

Thanks Colin, I would like to try everything I can before calling in the professionals. Spoke to HR Owen re the cost of an exchange fuel distributor - £600ish and no longer available...... Anyway I see how I get on at the weekend. Danny

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.

www.pelicanparts.com/techarticles/bob_tindel/911_inj_nozzle.htm Danny read the above link it may help. Jeff

Danny, I said professionals..... (sorry boys, only kidding) We can supply exchange rebuilt metering heads, or possibly a used one depending on your engine (180 or 204?), should it prove that you need one.

Colin - it's a 204, what sort of money am I looking at? Danny

Well after a few hours tinkering - this is what I have found. Firstly I drained my contaminated oil - and I am very glad I did. I was very thin and there was no doubt that fuel was getting into it. Interestingly more oil came out of the engine than the tank - I don't remember that being the case on previous oil changes. Than I removed the valve covers from the offending cylinder (which I am embarrassed to say is number 4, not number 1 as I said earlier. I blame the Bentley manual and the fact that the steering wheel is on the wrong side - I'm in the UK remember!). The camshaft lobes looked fine, very very slight scoring but after 143,000 miles you would expect some wear. Both clearances were a tiny bit tight - I could get the feeler gauge in halfway without undue force, so I adjusted them. Then I put the cam covers back on and filled the engine with mineral oil (well I wasn't prepared to waste another load of Mobil 1). I took the plugs out and spun the engine on the starter - oil pressure came up fine. As I don't have a leak down tester I thought I would try connecting the compressor to the offending cylinder and see if I could hear any air leaking out of the exhaust or inlet. With both valve closed the pressure built up, and there was no air leaking past the valves. However when I removed the oil cap I could feel/hear some air leaking..... I this stage I was getting visions of dropping the engine, rebuild etc etc. Anyway I then carried out a compression test. The engine was cold as I was unable to warm it up, I am not sure what impact this would have. No 1 140 No 2 145 No 3 140 No 4 125 (the cylinder that wouldn't fire) No 5 145 No 6 140 Now I know 125 seems a bit low but it is not drastically different (less than 15%). Remember also the cylinder has been thoroughly washed with fuel recently. I squirted some oil in the cylinder and it made no difference to the reading. Maybe things are looking up. So in went the plugs, and I fired her up with number 4 cylinder injector still blanked off. Well at least she still starts. The very last item on my list of things to try was to connect the injector pipe to a different outlet on the fuel distributor. I have metal pipes so this is a bit tricky, but I managed to connect number 4 pipe to the outlet for 5, and I blanked of number 4 at the fuel distributor. This was it... She started and when I pulled the plug lead there was a definite falter. I did the finger test to see if the exhaust manifold (header) was getting hot on number 4 and am delighted to say I have the blister to confirm it was definitely firing!!! No doubt about it - I have a fault on my fuel distributor So what are my options, someone on rennlist tells me that each outlet is individually adjustable - from what I can see he is correct again. I don't have any suitable graduated jars to attempt this today so I will leave this for another day. Has anyone ever dismantled one, or got one off a car that they can mail me some photos of, so I can get a better idea of what I am fiddling with if a do decide to attempt adjusting it myself? Or should I just get the unit rebuilt? Finally - can I remove it just by undoing the pipes and the 3 screws - or do I have to remove the whole mixture control unit first? Danny

A new fuel dist is about $500 in the US, probably more in UK. There's a good chance it's only "gunged up" (sediment) . If you feel confident in removing the top of the Fuel distributer, then get the Bentley manual, or get someone to email you the pages, everything must be surgically clean and be sure to not drop anything even a small nick can be a problem. Basically, it's take off the feeds undo the bolts lift and tilt so you can get your hand in to hold the bits,as you lift. but get a book. Now you are sure it is the F. D. you can try tapping the top of the F D near no 4. with everything connected. engine running. I didn't want to suggest this before as this will shake up and dislodge sediment in F.D. and had it not been the F D that would not have been a good thing to do. Then the best injecter cleaner you can find. Good luck. Sorry I don't have the Bentley for CIS. Jeff

Danny, I'm glad that you have found the problem, although I suspect that the engine is not going to be too healthy after all that fuel has gone through it. Mail me for prices of used and rebuilt units, I do have a complete 204bhp injection system available (somewhere...??) but the rebuild will be after the holidays now.

A dumb question maybe, but I'll ask it anyway just in case. 2.8i Capris used K-Jetronic if I remember right. As they are same number of cylinders, similar capacity, the metering head didn't happen to be the same part did it? If so chance of finding a cheap replacement must increase significantly. Chris

I am told that the metering head on the 81-83 SC is different from all other cars and that the earlier models used a more common type. I do have an 2.8 Capri Haynes manual (from my old TVR 280i days) and will have a quick look. Good thinking Danny

Chris, I have checked the Haynes manual - it is definitely different. Thanks anyway

Danny there is a Brand New Fuel Distributor for 1980 to 1983 3.0 911 for sale on the Pelican PArts BBS.....any good to you? http://forums.pelicanparts.com/showthread.php?s=&threadid=90850 >> Edited by nick-moss on Tuesday 24th December 09:52

Nick, That's the one! It's the first picture I have seen of the unit as it actually shows the adjustment screws. Danny

The rebuilt unit finally arrived and was fitted today, I haven't driven it far yet but it's definitely firing on all 6 cylinders again. The slight miss I used to have at idle is also now a thing of the past. I've got a long run tomorrow, so I'll hopefully find my warm start problem is sorted as well. Thanks for all your help, at least I diagnosed the fault even if I had to get the unit rebuilt by a specialist Danny

Danny Glad to hear all appears to be sorted now.

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