Non starting JX when hot.

[vag_glen]

Hi peeps, My 1988 Jx powered Karmann Cheetah has developed a problem, when it's been left over night or a good 6 hrs you get a good strong glow plug light and the van starts fine, but when the engine has cooled off a bit after running it will not put any power back to the glow plugs and start again!
The only way is to connect a piece of wire to the positive of the battery and touch the top of the gearbox end glow plug for around 5 seconds and the van then starts.
I've tested with a test light and multimeter and I'm getting nothing going to the glow plugs after the initial start up from cold.
I've replaced the glow plugs for new NGK units and also a new glow plug relay but no joy
So if anyone has any pointers on where to look next, ie broken wire? Bad earth etc etc.

Ta for now Glen.

[simoncummins]

Mine is the same. I am told that it is to do with the pump timing but i just live with it. As for glow plugs there is a sensor at the rear of the head that tells the plugs the temprature of the engine so when hot no power is sent to plugs. You can override this by disconecting the sensor or putting a resistor in the wire to fool sensor that the engine is cold hope this helps you. Simon.

[vag_glen]

Hi Simon, thanks for the reply, I know the sensor you mean and I'll have a look at that, I'm also getting my pump timing reset, so fingers crossed that'll also help.
Thanks

[noggintom]

Hello,

I have this problem too - I can start if I use the 'cold start' lever (or shall we call it the 'hot start' lever ). I have had the pump timed and this made little difference. I am wondering if it is because of old injectors giving a bad spray and making ignition harder. I am guessing my injectors are over 10 years old... Like you I have investigated the other things and glow plugs, relay and electrics are ok.

Let us know if you solve the problem - It would be great to know why it happens! Guess I have got used to using the cold start lever to advance the pump and this works ok so the problem has moved south on my things to do list!

Good luck,

Tom.

[bob senoj]

van-glen I don't want to kidnap your post but I was just about to ask the same question on the forum and noticed that your having the same problem.Yep when the engine is cold, mine starts first time every time -20 or +20 Celsius. but after running around and the engine reaches full temp, no way will it start if I switch off. I to have to wait for it to cool down and for the glow plug lights to show again on the dash, this could take hours, such a pain. I decided to have it checked out by a main VW dealer thinking if anyone can, they can.They said it was likely to be the pump timing so they adjusted it for me.£250 later, no progress still the same. Stated that the problem is with the injection pump. telling me that the vanes have worn, and they haven't got the pressure to pump the fuel up to the injectors when the pump and engine is warm/hot. But this diagnosis confuses me and I can't get my head round it, because if the vanes are worn and can't deliver the pressure then why doesn't this show on the engine performance, once the engine is running cold or hot, there is no miss firing or spluttering or loss of power from the engine. The engine will rev as smooth and sweet as a nut from low revs through to the cut off governor. Can anyone ex plane why worn vanes won't start a warm engine.
van-glen, have you been advised in this area, because I personally am not convinced, or too thick to work it out. Help is required on this JX gremlin.

[vag_glen]

Well guys I'm not so convinced about it being pump timing, I know for a fact mine will start by jumping from the positive of the battery onto the top of the first glow plug, which is just a case of the current being sent to all the glow plugs and heating them enough for the van to start.
So I'm more inclined to believe its the sender unit on the end of the head that sends the temp signal to the relay for heating the plugs, if that's not the fault I'm sure it's electrical based due to the jumping of the glow plugs I've mentioned above.
Bob for your sake I hope it's not the same for you after spending £250 on having the pump timing re set when it could have been a sender for a lot less than that!
I'm going to have a play around tonight and I'll report back

[ringo]

Quick to find out - as said previously, just disconnect the sensor and see if this fixes it.

I left mine disconnected and you have to count to 5 before turning the key as the light will not go out (due to disconnecting the sensor). Not a very elegant solution but one that works.

Far more elegant, as Simon says above, is to install a resistor inline with the sensor to fool the system to thinking the engine is colder than it is.
I can't for the life of me remember the value of resistance to put in though.

Good luck

Ringo

[vag_glen]

Well I've had a further look into this sensor, I found the one in question, the wire was almost broken off the terminal so I replaced that first, went for a 2 min drive, then left for 5 mins and as normal no glow plug light and wouldn't start.
So I removed the terminal from the said offending sensor, turned the key and had a glow plug light, waited 5 seconds and the van started like its never started in its life whilst I've owned it
So I'll be ordering a new sensor and see how I go from there, if it still plays up then I'll fit the resistor......or just leave it unplugged again!
Here's a pic to show which sensor,


As you look onto the back end of the head it's the one on the right of the cooling outlet, I know the picture shows different but that's due to the fact my vans a karmann and I get to sit inside the van in the warm and do my repairs
Thanks guys for the pointers!

Glen.

[colinthefox]

.....and the resisistor you will need is 470 or 600ohms. No special wattage rating, but make sure it's good and sturdy.

[ringo]

.....and the resisistor you will need is 470 or 600ohms. No special wattage rating, but make sure it's good and sturdy.

Nice one Colin