Help - Engine won't start

Paul Dunster · Jun 23, 2006

Hi All,
I put my SC back on the road in May and have done nearly 500 trouble free miles. Came back from PCGB mtg last week and put her in the garage no problem. Saturday I went to reverse her out of the garage for a wash and she just would not start!!!
Done the usual checks there is a spark at the plugs and smell of fuel in the exhaust. With ignition on I lifted the air valve arm and you can hear the fuel pump running. My thought is the cold start valve, tested the thermo switch and this is OK. As the CSV is behind the engine it will be very difficult to get out. When I do is there an easy way to test?
Should I be looking at something easier first?
Has anyone else had the problem?
Cheers,
Paul.

bones · Jun 23, 2006

Bad luck Paul, I'm assuming you have a fully charged battery and the engine is turning over.
I don't think it will be the cold start valve at this time of year the air is warm enough for a few cranks of the engine to overcome that. When you removed the plugs were they wet? If not and you have a spark then it is most likely a fuel problem. If the plugs are wet then the spark must be too weak, so suspect the coil in that case. Let us know the condition of the plugs.

Geoff_Fields · Jun 23, 2006

If you have a spark and fuel in the correct timing the obvious conclusion is flooding. I have experienced this problem with Bosch mechanical injection systems before on other makes of car e.g. Ferrari 328 and Ford RS Escorts. The cure was to disconnect the CSV by pulling off the electrical connection and leaving it that way. Starting problems never returned. It makes you wonder if the CSV is needed in our climate? Back in the eighties my local Ford dealership always disconnected the CSV on RS's and they never had any more starting complaints from their customers. I would still recommend getting an expert opinion on your specific problem.

Paul Dunster · Jun 23, 2006

Hi Bones & Geoff,
Thanks for the reply. Yes the battery is OK the engine spins just like normal. The engine is trying to fire but just won't start. I checked for a spark with a spare plug and there is a spark when spinning the engine. I lifted the air valve arm with the ignition switched on (you can hear the fuel pump running) and left it running for a few seconds, to allow fuel in, she was closer to starting but I didn't want to pour too much fuel in. My thought is that the choke is not pulled out (like in carb engines) and more fuel is required, hence my thought it was the cold start valve giving trouble. I have been reading the book and there are other things that are done to make the mixture more rich for starting, so need to investigate them also.

Geoff, it is not too easy to get specialist help as she won;t go, so not possible to take her anywhere. Anyway it is far to soon to give up yet, we have hardly got started in the investigation process, this is all part of the challange of ownership. However, I am still happy to consider any advise that comes my way.
My gut feeling is not enough fuel, rather than too much, previously she has always started on the first turn of the key but on Saturday even turning her over and over didn't get het started! I even left her and went back, with no success.

Has anyone else come across the problem who may have any ideas?

bones · Jun 24, 2006

Paul, you need to answer questions people ask on the forum such as .......When you removed the plugs were they wet?........otherwise we can't get to the next point of investigation, I have more possibilites in my head but until I know more I can't go further, cold start fuel pressure may be an issue, it often is on old CIS injected engines and would explain your hunch that the engine is not getting fuel. To be honest in this weather the merest hint of fuel and a 911SC engine will start right up if the spark is there. You say though that you can smell fuel, have you put your foot on the throttle when starting it? If so you may have flooded the engine but if that's the case the fuel should evaporate and it should start later with another try unless the plugs are really fouled (unlikely).
Give me a call Paul.

t11ner · Jun 25, 2006

Start by checking the spark properly!

Take the coil lead out of the dissy cap and hold it (with insulated pliars unless you are as brave as me [

]) about 5mm from a good earth. Get someone to crank the engine and slowly pull the lead away from the earth. The spark should jump at least 10mm. If it does, repeat this test using one of the outputs from the cap, ie put the coil lead back in place and use one of the plug leads but remember to expose the end of the lead (pull the rubber inslation back). If you get a significantly weaker spark out of the cap than out of the coil then you have a cap/rotor fault. Don't work about brightness, colour or any of those old wives tales - the only thing that matters is how far it will jump.

If the above is ok then follow the previous advice and whip the plugs out and see if they are wet or dry - if wet then dry them off, ideally with a blow torch, and try again.

If you don't fancy gettting the plugs out you could try disconnecting the fuel pump and cranking it to see if it kicks - this is an easy way of de-flooding an engine, it doesn't always work but it's worth a go.

Let us know how you get on [8D]

Paul Dunster · Jun 26, 2006

Hi Bones,
Point taken. Not had time to look at car over the week-end I was marshalling at an MGCC sprint yesterday and working in MG on Sat (bad news to have both cars dead!).
I had not removed a plug as tested with a spare. I will check this tonight and report back tomorrow.
Thanks for the assistance.

Paul.

Paul Dunster · Jun 27, 2006

Hi Bones,
I checked the spark at the plug as suggested by T11ner and the spark was jumping a measured 10mm gap. Then looked at the plugs, 4,5 & 6 were definitly wet with fuel. 1,2 & 3 not so obviously wet. I then turned the engine over with no plugs in and there was no signs of 'mist' comming from the plug holes although there was a good smell of fuel on both sides.
Paul.

bones · Jun 27, 2006

Well you've certainly done some good by blowing any flooding out of the spark plug holes but its a bit of a mystery why you have a good spark AND wet plugs and no ignition. I suggest you re-crank the engine One last time to blow out all the fuel, clean the plugs or fit new ones, check the dizzy cap for health, damp etc. and the rotor arm, put a drop of oil on the felt pad in the dizzy while you are in there everyone forgets that. Then remove the air filter cover and filter and push up on the sensor plate arm, you should here the fuel injectors 'whine' like a small jet (very cool sound), if you don't suspect the fuel pump. With a fully charged battery try again without using the throttle if it doesn't crank after say two or three trys put your foot on the throttle and hope. It sounds like you might have low fuel pressure, this could be down to a dead fuel pump relay or its fuse (buy yourself a new red relay as a spare) and replace the old fuse and clean the fuse box and relay contacts as matter of course. First check the fuse, then the relay, then finally the pump itself. If it still doesn't fire and they are ok then I 'd suspect the accumulator, or the fuel pump check valve. After that you might consider the Warm Up Regulator but 911SCs are easy to start if there is fuel or a spark one has to be not being delivered correctly. Try again and keep your foot off the throttle until you're sure you need to try for more fuel.

t11ner · Jun 27, 2006

I don't wish to contradict what Bones has written but if you have a 10mm spark going into and out of the cap then don't worry about the spark too much! If you had a faulty fuel pump or relay or low pressure you would be unlikely to have any fuel on the plugs or smell when you crank with the plugs out.

If some of the plugs are coming out damp then you are flooded to some degree so clean the plugs off with a blow torch, put them back in and crank it with the fuel pump disconnected. Use plenty of throttle and keep it cranking for a good few seconds - this will allow it kick on some of the fuel that is still in the cylinder. If it does kick, it will quickly die again as it runs out of fuel; if possible, re-connect the fuel supply as it dies (shove the fuse back in!) so that it doesn't cut out completely. If you can't do this in time then crank it again whilst it is still disconnected to make sure that you are shifting as much fuel as possible and then re-connect the supply and try to start it - again don't be afraid of using a bit of throttle, this will let air in and allow it to pick up and clear any remaining flooding.

Best of luck!

Steve

Laurence Gibbs · Jun 28, 2006

I would recommend you get hold of a proper fuel pressure gauge and check your fuel pressures as per either the haynes or factory manuals. One possibilty , check the air metering flap has some resistance, you could have a stuck piston inside the metering head. The flap will tend to move too freely if this is the case as there is no downward pressure from the piston. This will invariably flood the engine and it won't start. Other possibilities are a faulty accumulator/ fuel pressure reg , check your pressures and things will be clearer.

Guest · Jun 29, 2006

Just a thought:
Last year I had a similar issue when my Pop-off valve blew out. After temporarily re-attaching the valve it all started and I got home to re-apoxy the pop-off valve back on place.

The air box appears to need to be fully sealed. So just a thought has it backfired recently and could there be a crack in the airbox?

Hope this might help.

Paul Dunster · Jun 30, 2006

Hi Bones,
I gave the battery a long time with the charger and last night gave her another try. Still no sign of starting. I tried 3/4 times and then put foot down on the pedal but no go, however I whipped 2 plugs out and no sign of fuel on them. So as suspected it must be a fuel problem. I lifted the arm in the air valve, after removing the air filter and I can hear the fuel pump running. I know where I can get hold of a fuel pressure gauge so will start checking the fuel supply over the week-end.
Cheers,
Paul.

Paul Dunster · Jun 30, 2006

Hi SobeUK,
Good thought, however my car is a later one (1983) and has not got (or need) the 'pop off' valve.
Thanks for the thought.

Paul.

Paul Dunster · Jun 30, 2006

Hi Laurence,
I had already come to the conclusion I need to carry out a fault diagnosis of the fuel system. I will get hold of a gauge and fittings (the difficult bit) over the week-end.
I checked the 'air metering flap' it moves easily but feels like there is some resistance and it falls back down quickly, as if under a spring. I think the problem is not enough fuel rather than too much.
Thanks for the help.
Paul.

bones · Jun 30, 2006

Are you sure its not the CDI box you can here and not the fuel pump at all?
I assume you mean the 'sensor plate' when you say 'air valve' in which case when you push up on this you should here a loud jet engine like noise as the injectors prime. If you can here this then you have fuel but I suspect you are hearing something else because with fuel and a spark it should start. Keep us posted.

Paul Dunster · Jul 1, 2006

Hi Bones,
There is a high pitched whine as you turn on the ignition. When I lift the sensor plate there is a quiet roar which is coming from the area where the pump is. I checked the fuel flow tonight. I disconnected the fuel line into the accumilator (on the top nearest the side) and ran the pump, by lifting the sensor plate and then again with a 'jumper' lead in place of the red relay. In both cases there was fuel flow. The Bentley manual says it should be 1 litre in 30 seconds, I measured about 100ccs in 2 lots of 30 seconds. Could the pump run without giving the volume of fluid? Could this be the problem? Why would it suddenly not give the required volume? I will test the flow at the pump tomorrow to ensure it is not a blockage in the fuel line.
Cheers,
Paul.

bones · Jul 1, 2006

The whine is the CDI box for sure. I've heard the pump can flow fuel but not at the required rate, it seems unlikely that this fault would happen overnight unless your pump has reached a critical point in its life where it just can't pump the fuel required. Could possibly be a fuel filter or accumulator problem, do all the tests, if you have the equipment look at these
http://www.volvoclub.org.uk/tech/fuel_injection/k_jetronic.shtml
http://members.rennlist.com/jimwms/CIS/CIShome.html

t11ner · Jul 1, 2006

Sounds like you might be going in the right direction if you only get 100cc in a total pump time of 60 seconds!

If you have the facility, it would be handy to run the pump through an ammeter, it should run at about 5-8A with all the pipes connected and perhaps 3-4A if you have the supply pipe undone. If you don't get this change in amperage (or if the note of the pump doesn't change when you undo the supply pipe) then a restriction in the line seems pretty likely. Filter is more likely than accumulator but it would be pretty easy to prove by repeating the flow test at different points on the line.

You haven't jacked the car at any stage have you? Could there be a crimped pipe?

Laurence Gibbs · Jul 1, 2006

As you have disconnected from the accum and the filter is further along it's not going to be those. Your 100 cc's could have got there by gravity, though the one way valve "should" stop that possibility. So it looks likely to be something at the pump end. Do the obvious and check the cables for soundness and confirm you have 12v at the pump when it's supposed to be there. If all checks ok then remove the pump and try it with a spare bit of fuel line if you can, just to confirm that there is'nt a blockage in the pipe run up to the accumulator. You could also check the one way valve on the end of the pump (if it has one, some dont !). if all is still no go then it's a new pump. Without wishing to state the bloomin obvious, you do have fuel in the tank ? silly but ever so easy to do!