Won't restart if engine is hot...

[stephencoley]

Hi... Just want to pick your brains.

Got a 1.9 petrol water-cooled 1984 bus and we've had an intermittent fuel/starting problem pretty much since the day we bought her nearly 3 years ago. Basically after a long drive or in really hot weather our T25 struggles to restart if we've parked up for a while. Waiting for things to cool down (maybe an hour or so) has always got her starting again. I'm just really curious to know what is causing the issue.

Over the last couple of years I've replaced the manual fuel pump and push-rod, all fuel lines have been swapped, as have the fuel filter (many times!!!), but still the hot engine restart problem persists.

Also, is it normal to have 2 fuel filters fitted? Ours came with 1 just after the fuel tank and then another just before the fuel pump. Personally I can't quite see the point of the 2nd fuel pump in the engine bay, but I'm no expert. I did wonder if after stopping the engine, the heat from the engine bay could effect the paper inside the filter? Would the heat dry it up? Make it harder for the pump to suck the fuel through? I am completely guessing here The one thing I do know, is that we only get this problem when restarting with a hot engine.

I've been told an electric pump would almost certainly remove this issue, but I kinda like the simplicity of the manual pump. When it works!!! Keeping the manual setup also stops me having to meddle with electrics!!!

Any help???

[New Kentish Campers]

I'd certainly remove a filter where it's near a heat source and you could well be right in your thinking. Remove said filter, make sure the one near the tank is good and fit a new length of correct hose from tank filter to pump and try it again. Use proper fuel line clips, not jubilee clips. And make sure filter is the correct way round-usually has an arrow on it.

Maybe you could, once you've done the above, whip the top of the carb off if it still won't start when hot and see if you have fuel in the float chamber. At least then you know it's not starved of fuel. Replace the gasket too if you can, in case it tears when taking top off. As I know from experience... Gower and Lee sell them.

Good luck

[danmetallic]

Does she turn over? Could be the oilite bush at the end of the starter. Or the starter itself. (Someone will correct me if I'm completely off track)

[stephencoley]

Does she turn over? Could be the oilite bush at the end of the starter. Or the starter itself. (Someone will correct me if I'm completely off track)

Yep turns over. Just refuses to ignite, due to lack of fuel in the carb. I suppose one of the perks of having the extra filter in the engine bay, is being able to see if it's got fuel in it... And every time we've had this issue it's been dry. So something is preventing a new pump, battery & push rod from sucking fuel into the pump... The more I think, the more I feel the engine bay filter is not a good addition.

[CJH]

As was pointed out to me when I first got my van, that second filter just puts more hose junctions in the engine bay, increasing the risk of a leak - no need for it.

Have you checked the little conical filter inside the inlet spigot on the carb?

[Oldiebut goodie]

.. And every time we've had this issue it's been dry.

Surely this indicates the problem? (and the solution)

[fattmenn]

I have the exact same issue. I can drive for hundreds of miles without any problem. If I stop for a few hours and the engine completely cools it runs perfectly, but if I stop for a few minutes and try to restart when the engine is hot it runs badly and then stalls. The RAC have suggested servicing the carb. Did you find out what is wrong?

[stephencoley]

Not found a solution yet. My petrolhead brother in law has suggestion it could be a coil problem, but I'm still thinking it's fuel related. Had yet another breakdown today. Drove for about 8 miles, filled up with fuel, restarted, popped into Sainsbury for 10 mins, restarted, but didn't make it out of the carpark before the bus spluttered and died. Opened up the engine bay and the extra filter inside the bay was bone dry. Even though I was fairly confident she'd restart once cooled, I decided to give our breakdown people a go, just to see if they could throw any wisdom on the problem.
It took just over an hour for the breakdown folks to arrive, and during that time, as my engine cooled, I could actually watch the engine bay filter slowly fill back up with fuel. And surprise surprise when the breakdown guy arrived, the bus started fairly easily
As for any pearls of wisdom... He first suggested I'd put diesel in by mistake, then suggested a fuel blockage... I'm massively thinking that this is a vapour lock issue. And worryingly one that seems to be getting worse. Just not entirely sure yet how to cure this.

[danmetallic]

Not found a solution yet. My petrolhead brother in law has suggestion it could be a coil problem, but I'm still thinking it's fuel related. Had yet another breakdown today. Drove for about 8 miles, filled up with fuel, restarted, popped into Sainsbury for 10 mins, restarted, but didn't make it out of the carpark before the bus spluttered and died. Opened up the engine bay and the extra filter inside the bay was bone dry. Even though I was fairly confident she'd restart once cooled, I decided to give our breakdown people a go, just to see if they could throw any wisdom on the problem.
It took just over an hour for the breakdown folks to arrive, and during that time, as my engine cooled, I could actually watch the engine bay filter slowly fill back up with fuel. And surprise surprise when the breakdown guy arrived, the bus started fairly easily
As for any pearls of wisdom... He first suggested I'd put diesel in by mistake, then suggested a fuel blockage... I'm massively thinking that this is a vapour lock issue. And worryingly one that seems to be getting worse. Just not entirely sure yet how to cure this.

Well definitely loose the filter in the engine bay first, and replace the stock fuel filter. Double check breather pipes on top of the fuel tank also.

[fattmenn]

Mine has just gone again. Sat on double yellow lines waiting for her to cool down. Drove 200 miles with no problem. Stopped for five minutes and she started fine but stalled 200 yards down the road. I can't see any fuel in the engine bay filter either. If I find out what it is I'll be sure to post the solution on here.

[danmetallic]

Mine has just gone again. Sat on double yellow lines waiting for her to cool down. Drove 200 miles with no problem. Stopped for five minutes and she started fine but stalled 200 yards down the road. I can't see any fuel in the engine bay filter either. If I find out what it is I'll be sure to post the solution on here.

Have you tried any of the above yet?

[kevtherev]

If the fuel is running back to the tank then there's a leak in the engine bay.
If air can get in the fuel line gravity will take it to the fuel level in the tank.
Fuel pumps can leak via the diaphragm, lines from connections.

[dbz864]

interesting^^^^^^^^^,but why only when its hot

[stephencoley]

Well definitely loose the filter in the engine bay first, and replace the stock fuel filter. Double check breather pipes on top of the fuel tank also.

OK, dumb question time... I know where the breather pipes are situated, just not sure how accessible they are? Is this a jack & axle stand job? Also, how are the pipes attached? Can I just pull them out to inspect or are they more securely fixed
.

My rapidly improving mechanical know-how does have its limitations and this cursed vapour lock problem is beginning to stretch my little mechanical brain

Oh and... Stock fuel filter has been swapped. I've also checked exactly where my fuel lines are, just to check for any heat source issues. I've decided, for the time being, to keep the engine bay filter where it is (swapped for a new one though), as it's actually really useful to be able to see its fuel level (or lack of!!!)... When I do eventually solve this damn problem I'll lose the extra filter.

[kevtherev]

interesting^^^^^^^^^,but why only when its hot

One can assume that because heat causes expansion the problem magnifies.
Easy check
Measure the fuel delivery pressure from the pump.
Should be 2.9 to 4.3 lbf/in or 0.2 to 0.3 bar