As above really does my '89 m30 engine 535 have a cold start valve? Im having issues with the car constantly flooding and refusing to start properly. basically it has been laid up and only moved short distances for quite a while now so unsurprisingly the engines flooded. if i remove the spark plugs and leave them on the radiator for 24 hours then refit them and start the car with the accelerator pressed to the floor it will fire then catch and start but not on all 6 cylinders but won't rev at all and if the accelerator is raised from full on it cuts out. after it cuts out then thats it, it refuses to start until i pull the plugs again and dry them and allow the fuel to evaporate in the cylinders. if when i refit the plugs and remove the fuel pump fuse and crank it it refuses to catch no matter how long i crank it, but will cough and splutter with a small amount of easystart, once the fuel pump fuse is replaced we start the whole catching but won't rev then cuts out cycle.
the ignition system is in a1 condition and i have a good strong spark and the plugs are quite new. all hoses and pipework for the inlet system are brand new so no air leaks. im now believing the car is overfueling which is causing the flooding. after reading lots of info on the net cold start valves and thermo time switches keep getting mentioned on the m30 engine but i don't know if my year has one, i only have two connectors on the thermostat house but i gather there should be a third if i have a thermo time switch. another possibility is the fuel pressure regulator could be knackered leading to overfueling, ill have to check this tomorrow.
at the minute i just need to get it to start and rev properly so it will idle then i can start to look for the issue, so i was hopin to find and just disconnect the thermo time switch which would disable the cold start valve.
sorry for the long post but the cars been off the road for awhile while ive completed other work on it and now i want to get back to driving it so id be glad of any suggestions!
cheers
chris
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From memory the later engines are Motronic, and therefore have an ECU which does all the sorting out, so no cold start valve or thermo time. All done by the ECU.
I would not discount iffy plug leads. You may get a spark if doing an open test to earth, but put the plug lead back onto the spark plug and crank and allow for lowish battery, cold conditions, wet fouling, damp, cylinder pressures and you may not be getting a spark at the plug tip. Seem to remember there was an issue with damp and or cracked dizzy caps on these (and also the carbon tip in the cap can fall out !!!)
A good test for plug leads (over 5 years old???) is a damp fine (ironing atomiser) spray of water in low light over the coil, dizzy cap, and HT plug connection. Crank and see if you get sparks on the surfaces (can be quite a firework display) If so = change HT leads, or douse with liberal WD40.
Make sure any very small rubber pipes which go between air box, manifold. etc and tight and secure.
However once you ascertain HT circuits are top notch try starting with just a little throttle and not full.
Good luck
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thanks for the reply,
the battery is fully charged (has been put on charge nightly recently)
i get a good solid spark at the plug tip if it is connected to the ht lead and placed on the valve cover and cranked, i presume the same is happening when screwed into the head.
the resistance measurements for the leads are ok according to the info on autodata (no idea on there age though, would of thought failing leads would cause it to run rough not to fail to fire at all.)
the dizzy cap is in fair condition, ive cleaned all the points and there is no sign of any cracks.
i will try the fine spray test you suggested as i have a fine spray bottle i can use.
the only pipe on the whole inlet system i haven't replaced is the small thin pipe from the top of the fuel regulator which i presume is a vacuum pipe and may well cause an issue i'll get it changed this week anyway.
cheers
chris
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I don't know if yours does have a cold start valve or doesn't (although I suspect it doesn't)
If it does have a cold start injector, you'll have a blue coolant temperature sensor, AND a brown thermo time switch on the thermostat housing, AND a seventh injector, probably with a blue plug, somewhere on the plenum chamber of the inlet manifold.
If you have a cold start injector, check to see if the thermo time switch is jammed closed. Also, disconnect the electrical plug from the cold start injector, remove the injector from the manifold, keeping the fuel line attached, run the fuel pump - nothing, not a drop, should come out of the tip.
Is the air flow meter flap free to move? (sometimes after a backfire, they stick)
Has anybody had the top off the air flow meter (look for tell tale traces of silicon goo!)
If all is free, connect a voltmeter to the signal wire from the air flow meter, and move the flap slowly through its range - the voltage should increase smoothly as you open the flap.
From memory, if it's a 5 pin air flow meter connection, you'll have a live (probably 5Volts), an earth, an output for the CO adjustment potentiometer, an output for the air temperature sensor, and an output for the air flow meter flap position)
Do the injectors pulse properly? (your LED across one like you did with the coil should show you)
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i'll test the afm flap tomorrow, it doesn't show any signs of being tampered with.
i have 2 connectors on top of the thermostat housing, 1 green and the other blue i believe (don't quote me on that though), i did have a quick look for a seventh injector earlier and couldn't immediately see one but the lovely rainfall we've got at the minute is hardly helping.
cheers
chris
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You are getting other good useful advice, but I still come back to damp in the HT leads which are breaking down. ie old leads, car not warmed for a long time (to dry out). Yes you can get a good spark by earthing, but when connected to spark plug there is built in resistance in the plug for radio interference, and also under cylinder pressure the HT will rise and maybe break down before it reaches the plug (hence sparks you will see in low light under the bonnet). Worse under starting because the coil voltage is boosted.
Used to get loads of trouble with people who fitted a "sport coil" for extra power. Trouble was the HT leads broke down before the current could spark at the plug. BMW also fit carbon string HT leads for better radio interference which have a life of about 5 years
Had a Golf 2 and VR6 recently that defied starting. Tested with a fine water spray and had volcanic fireworks at turnover (higher coil voltage supplied) but not running.
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well ive been out to have a play this morning. firstly replaced the vacuum pipe from the manifold to the fuel pressure regulator, the regulator provides a good vacuum if you suck on the manifold end of the pipe so the diaphragm is intact so the regulator should be doing it's job. ive also replaced the small vacuum hose off the crankcase breather, all pipework within the inlet system has now been completely replaced with new parts.
ive checked the voltage at the afm and it raises smoothly to 4.4v with the flap fully open, the flap moves freely as does the butterfly valve in the throttle body. after replacing the plugs the car fired up and would rev to about 3k rpm then promptly died and flooded again.
something else i also did was to remove the two fuel pipes going into the fuel rail from the fuel tank, when you turn the ignition key on there was no fuel coming from either of them (i know it should only come from one, the other is the return, but i assume the pump priming should push some fuel through) does this indicate a fuel pump issue? (hoping not as the pump is buried below the false floor i made for my sound system)
cheers
chris
Edited by thomp1983 on 10/02/2009 at 13:13
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IIRC,the engine needs to be cranking on this calibration for the pump to be energized,not just the ignition on.
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it's alive, i've had the spark plugs sat on a hot radiator all week to fully dry the fuel out of them, and to allow the fuel to evaporate from the cylinders. i then cleaned up the distributor points with a dremel to a nice shiny finish as they were looking a bit dull, i then went back round all the connections in the inlet and fuel systems making sure they were all fitted securely, it then fired up first turn of the key with no throttle at all and settled to a near perfect idle. now just got a slight exhaust leak to fix and she's good to go
thanks for all the help,
chris
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