cerbera hot start problem

[jellie]

my early 4.2 cerb starts first time when cold and refuses to start when hot. When hot the engine turns over without firing and if it does start (which isn't very often) won't rev and dies.

So far we have changed/checked the following

plugs
leads
coil packs
crank sensor
engine earths
air flow sensors
fuel pump
fuel filters
ecu

It is a rebuilt engine having done less than 1500 miles and flies when its running so it does not seem to be a mechanical problem.

Does anyone have any bright ideas before I push the car off the nearset cliff?

[joospeed]

don't try and start it when it's hot?

it's a known point on teh early cars, that's why they routed the fuel pipes through the cabin on the later ones ..

[jellie]

When I say hot start I mean after driving it on any road for more than 5 miles it won't resart.

I can't jusy leave it to cool down because it takes over an hour to cool down which is a trifle annoying if i have just popped out to get a video. Do I reroute the fuel lines or is there an easier fix?

[SXS]

Dont play with the fuel system bud, unless you really have to - risky as hell... first thing to do, pay Joospeed a visit for a thorough check...

[jellie]

trouble is I'm at the opposite end of the country and no one has been able to find the problem. The strangest thing is that it didn't have the problem before the engine was rebuilt

[RUSSELLM]

How do these cars cold start, choke etc ?

[olly]

As Joolz says it's a known problem & is normally caused by the fuel evaporating in the lines before it gets to the engine. Get some heat shielding / shielding tape & protect the fuel lines with that & give it a go....

[rob_h]

Jellie

Just had a similar problem with my 96 cerb. Although mine started it would constantly stall. Did the same with leads, plugs etc but eventually turned out to be something corroded on the alternator and not kicking enough power through the system. As i'm not mechanically minded - i think they replaced something or did something to the alternator. Anyway - might be worth someone checking the output etc.

Not had any problems since this was sorted.

Rob

[gbbird]

Mine used to do this. I don't know if it was an early warning, but my starter motor packed up after a few months

[jonnie5]

I had a period of rough running, which also seemed to give me some issues with hot starting. This was fixed by changing a HT lead that was perished (it had got very hot!).

Probably doesn't help as you’ve already checked your leads...
.. but I'd thought I'd share it anyway

[andy4200]

Don't know if it's all related but... my car is an early cerb '96 and cut out a couple of times. I was stuck in a traffic jam in mid summer both times and put it down to fuel vaporisation. It was serviced shortly after that and the HT leads were changed as one was virtually melted. Haven't had a problem since.

Only other thing that looks a bit iffy is when it's real hot and the oil pressure is down around 20 psi. This only happens when the oil level is less than max. It sounds like my old 'dipstick at the back' is none too accurate.

[kojak]

[quote=andy4200]Don't know if it's all related but... my car is an early cerb '96 and cut out a couple of times. I was stuck in a traffic jam in mid summer both times and put it down to fuel vaporisation. [quote]

Mine would cut out after restarting when hot, but I increased the tickover slightly to around 1000 rpm. Fine now.

[jellie]

thanks guys that gives me a couple of items to try.

My oil pressure also drops to 20 when hot as well but only on idle. i am using mobil as i guess are most people. I have heard that race engineers often recommend thicker mineral or semi synthetic oils to reduce the oil thinning problem when hot. Could this also help with low oil pressure?

On the subject of oil levels i discovered if i brake very very hard on a steep downhill slope the oil pressure drops to 0 and the orange warning light comes on for a second-not good. I now tend to check the oil with the car parked on the drive which has a slight downhill slope and, i guess, overfill it slightly-this has cured the problem.

[SXS]

jellie said:

thanks guys that gives me a couple of items to try. My oil pressure also drops to 20 when hot as well but only on idle. i am using mobil as i guess are most people. I have heard that race engineers often recommend thicker mineral or semi synthetic oils to reduce the oil thinning problem when hot. Could this also help with low oil pressure? On the subject of oil levels i discovered if i brake very very hard on a steep downhill slope the oil pressure drops to 0 and the orange warning light comes on for a second-not good. I now tend to check the oil with the car parked on the drive which has a slight downhill slope and, i guess, overfill it slightly-this has cured the problem.

Oil pressure spring - Joospeed can sort this out - he has a special spring that increases pressure... also might be an idea to check the oil pan and make sure the baffling is intact...

Thicker oil is good - but not always - depends on your driving style - I'd recommend either a 10/50w or 15/50w... Amsoil stuff is great...

[trooper1212]

jellie said:

thanks guys that gives me a couple of items to try. My oil pressure also drops to 20 when hot as well but only on idle. i am using mobil as i guess are most people. I have heard that race engineers often recommend thicker mineral or semi synthetic oils to reduce the oil thinning problem when hot. Could this also help with low oil pressure? On the subject of oil levels i discovered if i brake very very hard on a steep downhill slope the oil pressure drops to 0 and the orange warning light comes on for a second-not good. I now tend to check the oil with the car parked on the drive which has a slight downhill slope and, i guess, overfill it slightly-this has cured the problem.

My 96 cerb is exactly the same on both counts, I wouldn't worry about it. The oil pressure has been low on idle for the past 14,000 miles since I've had her, and probably for most of it's 40,000 miles, and it's still going strong.

As you say, overfilling cures the pressure drop to 0, but if it only does it when warm, you may want to check your idle speed. If your hot idle is too low, the oil pump will shut itself down.

[kojak]

As Ash has said, change the oil pressure spring.

[trooper1212]

kojak said:

As Ash has said, change the oil pressure spring.

It's the first thing to do certainly, but I've had mine changed and it makes no difference. Oil pressure is good across the rev range, just low on idle.

[andy4200]

trooper1212 said:

kojak said: As Ash has said, change the oil pressure spring. It's the first thing to do certainly, but I've had mine changed and it makes no difference. Oil pressure is good across the rev range, just low on idle.

Mine made no difference either and it was Joolz that changed it last timme I was down there....

The other week I overfilled a bit (half litre or so) and my pressure at idle is up around 28 psi now. But my 'working' pressure is still no change at around 55 psi.

A thread the other day suggested that the old dipsticks at the back may tend to over read the oil level so I'm wondering if my overfill was maybe more like what should be put in normally.

[J_S_G]

andy4200 said:

The other week I overfilled a bit (half litre or so) and my pressure at idle is up around 28 psi now. But my 'working' pressure is still no change at around 55 psi.

On hot days when I've been caning the Tusc, the oil pressure in the S6 at idle drops to 6-7 PSI (and that's since the rebuild as well as pre-)! No help, I know, but an uninteresting aside, nevertheless...

[trooper1212]

J_S_G said:

andy4200 said: The other week I overfilled a bit (half litre or so) and my pressure at idle is up around 28 psi now. But my 'working' pressure is still no change at around 55 psi. On hot days when I've been caning the Tusc, the oil pressure in the S6 at idle drops to 6-7 PSI (and that's since the rebuild as well as pre-)! No help, I know, but an uninteresting aside, nevertheless...

The old rover V8 in MGs that we used to play with, they were quite known to have almost 0 psi at idle. Rev the engine to 3000rpm and make sure the oil pressure picks up to a good rate, and then rev past that and ensure that it builds in relation to revs. If that is ok, then the engine is almost cetainly fine.