Steven McCarthy Posted November 12, 2021 Report Share Posted November 12, 2021 Can anybody help advise I have a 1971 TR6 CP. After driving for approx 1hr the engine cuts out and then will restart but only run for 5-10 minutes. I have checked the following and all are fine; Ignition fine Fuel pump and pressure fine Blown fuel line out back to tank no blockages It would seem this is perhaps heat related or could it be a split diaphragm in the MU. Would really welcome any ideas please. Quote Link to post Share on other sites
astontr6 Posted November 12, 2021 Report Share Posted November 12, 2021 15 minutes ago, Steven McCarthy said: Can anybody help advise I have a 1971 TR6 CP. After driving for approx 1hr the engine cuts out and then will restart but only run for 5-10 minutes. I have checked the following and all are fine; Ignition fine Fuel pump and pressure fine Blown fuel line out back to tank no blockages It would seem this is perhaps heat related or could it be a split diaphragm in the MU. Would really welcome any ideas please. When the engine cuts out have you checked for a spark? Coil or condenser could be suspect or power supply? I assume that you can hear the pump running when engine has stopped? Bruce, Quote Link to post Share on other sites
BlueTR3A-5EKT Posted November 12, 2021 Report Share Posted November 12, 2021 (edited) Does the fuel tank vent ok? Open the fuel cap when the car cuts out- is there an inrush of air to the tank. Is there a small hole pierced through the rubber seal in the tank cap? That is the tank vent. Not on Carb tanks but should be on PI as there is no other fuel tank vent to allow air in as the fuel goes out. Is the - ve terminal of the coil connected to the white/black wire that goes to the distributor? White wire from loom connected to +ve terminal on coil Edited November 12, 2021 by BlueTR3A-5EKT Quote Link to post Share on other sites
Steven McCarthy Posted November 12, 2021 Author Report Share Posted November 12, 2021 I have checked coil and condenser and have got a spark, must Amit did not check if pump was still running will do that next time. Have opened the fuel cap but not checked for a small hole through rubber seal will also look at that - thank you both for your ideas much appreciated. Quote Link to post Share on other sites
ntc Posted November 12, 2021 Report Share Posted November 12, 2021 If the pump is stopping safe bet inhibitor switch Quote Link to post Share on other sites
John Morrison Posted November 12, 2021 Report Share Posted November 12, 2021 Hi Stephen, I have re-titled yur thread. to hopefully encourage more targeted replies. John. Quote Link to post Share on other sites
Mike C Posted November 12, 2021 Report Share Posted November 12, 2021 Open the fuel cap immediately it stops and it there's a rush of air and the engine starts it's the tank venting but the last time I had these symptoms it was a defective coil failing when it heated up- like most intermittent faults it was a horror to diagnose-I hate attempting to fix problems by just replacing parts. Quote Link to post Share on other sites
BlueTR3A-5EKT Posted November 13, 2021 Report Share Posted November 13, 2021 20 hours ago, ntc said: If the pump is stopping safe bet inhibitor switch Yes, good point. The inertia switch contact is simply a ball bearing inside a plastic tube sitting on two brass contacts, which get dirty over the year. If fitted it looks like this Quote Link to post Share on other sites
Tim D. Posted November 13, 2021 Report Share Posted November 13, 2021 You can temporarily bypass the safety switch if you need to check. I have had a similar cutting out issues in the past and causes have included. The brown cables at the starter being loose meaning all power is lost, and a broken wire behind the ignition switch. Worth checking those brown wire connections cheers tim Quote Link to post Share on other sites
Tom B Posted November 13, 2021 Report Share Posted November 13, 2021 1 hour ago, BlueTR3A-5EKT said: Yes, good point. The inertia switch contact is simply a ball bearing inside a plastic tube sitting on two brass contacts, which get dirty over the year. If fitted it looks like this I am not sure that these old inertia switches are good for the current drawn by the Bosch/Bosch replacement fuel pumps, which is much higher than the original Lucas ones. Mine was all a bit melted inside and as Blue says, pretty corroded and nasty. Consider a modern replacement! It is best (if not already done) to run the pump through a relay and put the inertia switch on the low current side. Quote Link to post Share on other sites
PodOne Posted November 13, 2021 Report Share Posted November 13, 2021 Already mentioned but I had a similar problem years ago with a faulty ignition switch which would heat up cut the ignition then cool after 5 minutes and restart only to cut out again in short order as its contacts got back up to temperature quicker. Try giving the wires a wiggle and measure the voltage at the switch without removing or moving the key. Best of luck these are the worse kinds of faults. Look forward to the actual cause. Andy Quote Link to post Share on other sites
Mk2 Chopper Posted November 14, 2021 Report Share Posted November 14, 2021 I've had this symptom, mine was the coil. I've also had something similar in an old VW where it had a gauze filter in the tank which has broken down and some debris was getting sucked onto the outlet, as soon as the pump was off it would float away and would run again. Sounds like yours is something to do with the heat and could be cavitation if it's not the coil or pump stopping. Gareth Quote Link to post Share on other sites
paul.taylor6 Posted November 14, 2021 Report Share Posted November 14, 2021 I had same problem with ignition switch. Found out when I knocked steering column the engine would cut out as switch on column. Paul Quote Link to post Share on other sites
cp25616 Posted November 15, 2021 Report Share Posted November 15, 2021 Sounds like a coil to me too, ask me how I know? Just stick a coil on first and see what happens. When the car is warm enough where it failed before and still cuts out then that's that eliminated. Its all about working your way through the problem in a logical manner really. Alan G Quote Link to post Share on other sites
JohnC Posted November 15, 2021 Report Share Posted November 15, 2021 5 hours ago, cp25616 said: Its all about working your way through the problem in a logical manner really. Totally agree. So an MU diaphragm? No way. That would give you grief from when you first turn the key. What changes after an hour (and in what conditions?)? Electrics heating up seems most likely. But is it always an hour? Or just "quite a while"? I had a piece of plastic (like supermarket bag) in the tank and it blocked the fuel flow every so often. And it clogged up quickly after a brief stop. I guess it got sucked into the tank outlet soon after startup. It was an absolute bugger to diagnose! Is your fuel filter clogged? How long must the car sit before it will run for another hour? Until cold? Then temperature is a likely problem, so the suggestions re coils etc make sense. Seems random? Then maybe a loose electrical connection, or a fuel blockage. But a PI problem? Not so likely. Keep posting here with what you find. Plenty of folk here to help. John Quote Link to post Share on other sites
cp25616 Posted November 16, 2021 Report Share Posted November 16, 2021 Oh just to carry on from checking the coil first, if its not that then try a different inertia switch (as mentioned above).Recently my previous TR6pi developed a problem with intermittent cut out either stopping or just before the car stopped entirely it would return to normal ? Turned out to be a faulty inertia switch. So coil first and then inertia switch and if neither then you have eliminated the two most obvious things to point a stick at. Alan G Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.