Youcef

I have been slowly developing a problem with hot starts on my car, hope you guys can guide me.

Over the past few months this problem has been increasing, I have searched Adrians book, looked into the Bentley and searched the forums and have come up with the some places to look.

Baiscally the car starts fine when cold, runs rough but fires and runs every time. When it is hot and stopped for longer than 15 mins it will not start easily, when you hit the starter it fires and dies after 2 secs, after that nothing, not even a fire. You have to put your foot to the floor to get it to fire, it then fires on 1 cyl after about 3 runs on the starter of 30 secs, then slowly 2, then if you pump the gas it finally fires on all 6.....it then idles rough as it has always done.

My reaserch has led me to start looking in the follwing, if you can guide me differently your help would be appreciated.

1 - Injectors...I am pulling these today and having cleaned.
2 - Cold warm up switch, apparently if this fails it can cause rich starts.
3 - Residual fuel pressure....have no idea how to check this.
4 - Fuel pump operation....I am gonna check they both run right.
5 - Idle mixture....I read this could cause difficult / hard hot starts ( should I be lean or rich, what AFR should I have on idle?)

Any other things you think I need to check? You can rul out the AAV it is new, is there any easy way to check WUR? Can it cause this?

Thanks

fritz k.

hi youcef,

i had a very similar problem with my car, it was caused by that temperature sensor which controls the warm-up-valve. i think, it is no. 2 on your list.

in addition to that i would check whether leak air causes that idle problem. e.g. check whether the 12 nuts of the intake manifold are tightened correctly.
the nuts tend to loosen, maybe due to shrinking of those plastic material flanges between manifold and cylinder.

fritz

underpsi

it sounds like a similar problem i had, it turned out to be a intake air leak.

l clark

ck for something loose between turbo and throttle body.mabey even o ring @ throttle body

nathanUK '81 930 G50

Hi Youcef,
what about the fuel accumalator ? That can cause difficult hot starts.

Youcef

Hey all,

Thanks for all your input, I am still working on it.

Fritz, I tend to suspect this cold start sensor, anything with a bimetalic strip older than 5 years has my vote for a failure, not easy to get at this one though, looks like I need to pull the entire jetronic system. I will order the part and then replace the sensor. You were also correct on the intake manifold being loose, all the nuts were "soft" with some loose, visible fuel leakage around number 1.

Under psi & I clark, thanks for input, I firstly checked for a hiss, orange ring or any vacumm or manifold leaks....nothing there. Thanks.

Nathan,

Thanks for the info, second thing on my list to look at today was the accumulator, do you know how to test it?

I ended up pulling all the injectors today and taking them to Bosch to get cleaned, they all were looking about the same with a couple more sooty than the others. I also pulled all the plugs today, even the deaded number 6, removed the tin and had them done in about 45 mins. All the plugs looked great, not oil, no soot, just number 3 was a little more white than the others. I was concerned about number 3 bust it may be the result of a prefft hard track day yesterday.

I am gonna need to wait for the injectors so I will change the brake pads on the rear as the sensors burnt in the track day and then maybe pull the accumulator to at least know what it is that I am looking at.

Thanks again.

Anu input on testing residual pressure or accumulator operation would be most appreciated.

nathanUK '81 930 G50

The reason it would be difficult to start is that it doesn't hold fuel pressure. The heat of the engine then causes that fuel to evaporate in the lines and then you get vapourlock ?
I hope someone knows if a gauge can be hooked up somewhere. My guess is it needs to be between the accumalator and the fuel head, before or after the filter shouldn't matter.

fritz k.

hi,

to fix the problem iīve replaced the temp sensor on the right hand site below the fuel distributor

you are able to get to this if the airfilter housing and the intercooler were removed.

i have a description regarding the measurement of fuel pressure. unfortunately it is in german language. if it would be helpful, i could send you a scan.

fritz

Youcef

Fritz,

Thanks for the reply and the effort to post the pics, appreciated. I am a little confused, according to Adrians bbok and the "Without guesswork" manual part number 46 (part # 93061711800) is the thermo time switch on the 94 3.6 used to control the operation of the cold start valve, are you talking about something else?

fritz k.

hi youcef,

seems that i was wrong. as far as i remembered the faulty sensor controls the WUR. actually it must have been the 35 C switch, which delivers data to the lambda control unit. sorry for confusing you.

fritz

Youcef

Just thought an update on this issue / issues would be nice.

The rough idle I was feeling has been sorted with and injector clean, seems a few injectors were stuttering and after cleaning they flowed cleanly and idle was a solid 850 rpm. The tech told me they were no exactly all balanced as far as pattern goes but as good as could be expected.

The hot start problem persisted until I changed the accumulator, problem solved with no start issues, no need for any throttle just as intended I guess. Not a very difficult job to change the accumulator but you do need to get back there with a torch and come mirrors to help you out.

Anyway car is running fine again, thanks for all the help.

nathanUK '81 930 G50

Cool

mcjack

...just to swap the injectors to some larger sizeīs.
It was a one-time invest and the car is running fine now for more than 4years without cleaning the injectors every year. Especial here in ME it helpīs keeping the engine-temp cooler due to more fuel in the comb.area and coolīs the pistons also.
Had some disc with one of the HOC-guys about it and he came to my place and it took him only 30 minīs to fine-tune it. Now the Engine feels stronger and the throttle responce is amazing!

paul_23

Hi mcjack

Are you running a 3.6Turbo and if you are, what injectors did you replace them with?

Paul

mcjack

It was orig 3,4 but is upgraded to 3,6 & Turbo+spring.
The fuelpressure is original and the largersize Injectors I bought in the US.
Iīll try to find the bill with the numbers and mail it to you.
But the guy at HOC (who fixed it last summer) knows where to find these cheaper -if only somebody knows his contact mail or phone.
Not sure but he was in contact with evoms or sharkwerks ? He also changed disconected the temp-sensor and used a resistor when he tweaked it. Sounds weared but the result is more than OK
He also used a PDA and checed the CO on idle and running under load (street).
AND now I donīt drop this car at the dealers anymore - they just donīt know how to do it.
Donīt the guys at the dealer or HOC know about this?