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Triumph TR6 - Cutting Out TR6 PI

Any hints on a '71 TR6 cutting out on hot (UK in October!) days, even though fitted with a Bosch pump conversion? Cut out is total and preceded by higher pitch/louder pump sound. Fuel elevel seems to make no difference.
Waiting 5-10 minutes allows a start and then all seems OK for a variable time (up to 50 miles so far).
Thoughts so far... blocked pressure reg or filter, or fuel line getting hot enough to heat soak.

Thanks in advance,
D.H.
David Hill

David
Try by-passing the roll-over cut-out switch (on the bulkhead next to the wiper motor).Cant see why this should be temperature dependent but iut is a known cause of cut-outs.
Peter Cobbold

check that fuel pipe outlet from your tank is not blocked.Where is your bosch pump situated,deep in the left hand side of the spare wheel well,these pumps like to have a good level of petrol above them.
Simon

The conversion has clearly been professionally done. The pump is in the left side of the spare wheel well, beneath a Bosch filter.The connections are in stainless braided hoses, with coloured anodized fittings.
The only part I can't identify is in the line out of the pump. This is a clear plastic or glass fitting with chromed ends and a chromed centre tube.
I doubt the filter will be blocked after 6,000 miles so I plan to strip the pressure reg., which I believe has a strainer which could be blocked or partially blocked.
The only other thing I can see is that the fuel lines run close to the exhausts under the car, above the closing panel welded to the bottom of the chassis. This makes me wonder if heatsoak here could be a problem and I'm thinking of putting in some reflective mat around the fuel pipes.
Snag is, this car has been left with me to fix and I haven't yet been able to make it misbehave. All I can say is that the problem is apparently heat related and the system behaves just like an overheating Lucas-pumped system.
Again, any further ideas or comments would be appreciated and I'll let you know the outcome.
Many Thanks for the replies so far,
David Hill
David Hill

Dave,

the glass filter may be the problem,causing resistance to the prv,there is a product advertised in tr action, it is basically a bandage that you wrap around the exhaust manifold,maybe you could use this to wrap around the rear silencer this should keep heat to a minimum
simon

Thanks, Peter and Simon,

I believe that I have found the problem, with the help of Mike Pumford, of the PI specialist of that name in Wallasey.
Mike said that they run race TR6s with a big, single centre exhaust which goes even closer to the fuel line in the centre of the chassis and have never had vapour lock problems because of that, even under racing conditions.
It turns out that a batch of repro fuel fillers was made without a vent hole. I popped the cap and the 'top hat' rubber seal was entirely hole-free. So, given the high flow of the Bosch pump, it is feasible that the system would end up trying to pull against a substantial vacuum, hence fuel starvation. This would agree with the fact that waiting a while after a halt would allow this vacuum to ease. Speaking to the owner, I found that the first cut out came at 120 miles and a 5-minute wait let the car go on 50 miles. A further half-hour wait let the car get to York without problems. This seems to fit the pattern, espcially with the system having an air outlet in the filler neck and no other obvious breather system.
So, I took off the rubber and drilled a hole in the backplate, right at the edge of the high part of the 'top hat', punching a hole in the rubber seal at the same point. Using a mini-Maglite, I was able to inspect the inside of the tank, which appeared quite clean.
Proof of whether this has worked will be available when the car is driven back down south on saturday. In the meantime, I am going to replace the inertia switch on the bulkhead anyway-it has a poor action and doesn't pop up when tapped.
Incidentally, the mysterious, inline glass housing doesn't have a filter inside, just a chromed tube with a 1/4" hole. All I can think is that it might be some sort of telltale or pulse-smoother, or that its filter element has been omitted because there is a Bosch 'tin can' filter in the line.
I'll post the outcome when I hear how it turns out.
Grateful thanks for the advice,
David Hill
David Hill

The final analysis. The TR6 ran perfectly the 120 miles to its destination-clearly the unvented fuel cap was the problem. In fact, the only sputtering occurred when the family friend whp was returning the car ran out of fuel-just outside a petrol station.
Thanks to all of you who mailed me with suggestions.
David Hill
David Hill

This thread was discussed between 12/10/2001 and 23/10/2001

Triumph TR6 index

This thread is from the archive. The Live Triumph TR6 BBS is active now.