740 GL B200E K-Jetronic intermittent starting problem

[Munty]

Ok, I've checked the past posts and can't find this problem exactly so I'm falling on the mercy of the forum wizards. I've got a great '88 740GL 2.0L that has +250K miles (don't know exactly since odo stopped working a few years ago. So few problems it makes me despise most modern car mfrs, but alas an intermittent fault has now arisen with the constant injection system;
The engine sometime starts fine, sometimes not. Getting more often the latter now. Hot starting fine. Fuel pressure ok, sparking ok. Cold start injector ok. Individual cylinder injectors not ok.
They seem to do one squirt on initial cranking and that’s it. The car will eventually start with lots of short cranks to build up enough fuel, but battery sometimes gives out. I’ve lifted the metering flap whilst cranking and the injectors then deliver plenty of fuel. So it looks like an intermittent electrical problem to do with the CIS fuel system, but the manual just says take it to the Volvo dealer. Has anyone got experience of this and any advice please?
Thanks, Matthew.

[stephend]

AFAIK, there's no electrical aspect of the injection system that could have the effect you describe. If lifting the metering flap restores the fuel flow, my first guess would be that it might be a problem with the flap sticking - maybe if there's a lot of crud around the flap itself, or back towards its pivot. Perhaps it sticks more when the engine is cold?

The cold start injector is one obvious suspect, but you say it's ok, and in any case I think it has to be really cold for this to kick in. The auxiliary air bypass valve could also be a problem, though I'd guess not in this case.

Is the cold starting the only running problem?

Edit: you might need to find a K-jet specialist for this one. I think there used to be a Bosch fuel injection service centre in Coventry; might be worth seeing if they're still in existence and able to help?

[cumbrianmale]

Worth having a poke about on k-jet.org

[Diesel-do-nicely]

Originally Posted by Munty

Ok, I've checked the past posts and can't find this problem exactly so I'm falling on the mercy of the forum wizards. I've got a great '88 740GL 2.0L that has +250K miles (don't know exactly since odo stopped working a few years ago. So few problems it makes me despise most modern car mfrs, but alas an intermittent fault has now arisen with the constant injection system;
The engine sometime starts fine, sometimes not. Getting more often the latter now. Hot starting fine. Fuel pressure ok, sparking ok. Cold start injector ok. Individual cylinder injectors not ok.
They seem to do one squirt on initial cranking and that’s it. The car will eventually start with lots of short cranks to build up enough fuel, but battery sometimes gives out. I’ve lifted the metering flap whilst cranking and the injectors then deliver plenty of fuel. So it looks like an intermittent electrical problem to do with the CIS fuel system, but the manual just says take it to the Volvo dealer. Has anyone got experience of this and any advice please?
Thanks, Matthew.

I have 10 years of this system on early vw,s if this was a golf/scirocco mk1 . The multi turney thing with the key was often just the ignition barrel contacts wearing out.
Also, the fuel pump relays were very suspect, they are triggered by the hall sensor , sending around 2-5v to the very smallest pin on the relay, this in turn activated the big terminals.
Dozens of times the relays overheated and melted the fuseboard from poor contacts.
The cold start valve, on the block with the 2 pipes going to it has a wire mesh at the unions, this gets blocked with rust, back flush with carb cleaner.
the fuel pump should whir all the time during cranking.
After a five minute idle pull the injectors out, see if any leak down over a few hours, k-jet injectors must spray a fan mist, if it is like a water pistol in any way they are nackered.
New injectors are worth easily 25 % mpg and 20% power over 150000 mile ones. No cleaner will dissolve rust, dont waste money.
Dont poke a long allen key in the mixture screw hole and fiddle with the dis flap. you will not acheve anything, apart from being a wally.
If there is rust in the tank, get a plastic in line filter, cut the fuel pickup pipe back and fit the filter, about 1cm higher up than original, then put a old loudspeaker magnet in the tank below the filter opening, all the rust will stick to it and ypu wil get clean fuel through to the new fuel filter you will fit, the accumulator is a sprung diaphram, it evens out the fuel pump pulses, clean it thoroughly. Make sure the earths are good, there will be a castle typr block near the fuseboard bolted to the chasis, there will be another near the headlamps. clean and crimp any wobblies. I have had a kjet scirocco earth through the throttle cable and the starting fault was as you mention.
There is no owners club trick, methodical sherlock homes type elimination only. But start with the relay, and take it from there. Mesage me if you get stuck or need more ideas. cheerie, Andy

[rustytoba]

If the flip is a little reluctant to move, it may not just be dirty, the flap need suction from the engine to make it move in the first place, so it may be because the large rubber bellows may not be fitted properly or the large jubilee clip has become loose allowing any air sucked in by the engine to bypass the air/fuel distributor altogether.

The K-jet system is almost bulletproof, but simple thinks like loose hoses/piping/wires (all easily overlooked from time to time) can bring the whole thing crashing to a halt.

Rusty

[Munty]

Ok, thanks to all for the comments and suggestions. I have not worked on the car again since away from home Mon-Fri, so planning to get her back on the road again this weekend. But I have a hunch it may be the coil. This is my reasoning;
Whilst I have been cranking the car with the bellows off the engine has never fired. I'm sure that it would since the problem is intermittent and I've cranked it loads of times. This implies it won't start due to lack of fuel (although it does a single shot when initially cranking –a feature I guess). It does inject if the flap is lifted, but the flap won't lift with the bellows off since there is no air drawn through the metering system to lift it. If I put the bellows back on and crank the airflow should be enough to lift the flap and she'll start (intermittent problem still there of course since nothing's changed).
Reason for my hunch;
When the intermittent problem occurs the engine gives a shudder when I stop cranking (like one cylinder fires as it comes to rest). Now that sounds like a LT coil supply cut causing a HT spark (like a good old set of points). I've got a spare coil so easy to check. It could be the hall effect sensor (again) -I had to replace the distributor 8 years ago since this failed and on my car it's a non-serviceable part. Could also be the ignition module.
When I was testing a spark plug and it sparked fine the fault was not occurring and the engine would have started, save for the fact that I also had the bellows off so no fuel injected.