Engine cuts out when warm

[njc]

Hi Folks,

 

I have a problem with my TR6 after its winter laid up in the garage.

 

Running the engine it started with no problem. I left it running as I hoovered the carpets and pumped up the tyres. It then started to run rough and cut out when warm. Whatever I did it would not restart. It was turning over fine but just wouldn’t fire. I left it a while to cool down and it started again after a bit of coaxing but then cut out as I tried to drive it back into the garage. Engine turns over but there is no spark or too much/too little fuel.

 

I’m obviously reluctant to take it on the road until I can sort this problem out.

 

It seems to have some temperature related problem.

 

Last year it cut out on me on the first run of the year on a hot day but a thought it was to do with rust in my tank. I replaced the tank with an ally one thinking this was the problem. It was fine all summer after this. I am now thinking this wasn't the problem.

 

I have an electronic ignition system inside the distributor. It's a PI CR series car with a Bosch fuel pump.

 

So my questions

How do I determine if it is electrical (Elec ignition) or fuel system?

I was going to refit the original points to check. Is there anything else I can check?

 

If it is fuel system, I suspect either PRV or metering unit. Is there a way to check or zone in the problem?

 

Many thanks

Neil

[RogerH]

Hi Neil,

try another coil as an easy elimination. Do you need a special coil with the electronic ignition.

 

Roger

[Stag powered]

I have had problems with damp in the distributor condensing on the cooler cap and rotor arm as the engine warms up after a long lay up, and this shorts everything out, baffled the hell out of me when it happened. Check all your ignition related wiring, corrosion after a lay up creates all sorts of agro. It is unlikely to be an injection problem

Neil

[rodkaz]

try changing the rotor arm may help regards rod

[tr6tuga]

I had these trouble And the end result was a faulty coil....they can be very ....sensible,

Now always have a new one ready for switch

[DIYBOSSCAT]

Hi Neil,

take a plug or plugs out, if they are wet then they are not sparking properly. Take the centre HT lead off the dis cap and hold near to earth, turn engine over - do you get good constant sparking. If spark is ok, then all that is left is cap/rotor arm/leads and plugs. Iff plugs are dry and sparking ok then its fuel related.

Hope this helps.

 

regards,

 

Vince.

[Nick Jones]

Rotor arm. They crack where they fit over the shaft. The crack opens up when the shaft warms and closes when it cools.

All the currently available black rotor arms (whatever is on the box) are suspect. Invest in a red one from Dizzy Doctor, Rarebits for Classics etc.

 

Nick

[Tony Millward]

Have you put some fresh fuel in?

 

Tony

[njc]

Thanks chaps!

 

I'll start by checking the rotor arm, coil and dizzy cap. I hope it isn't fuel related

 

I haven't put in fresh fuel yet since i want to adjust the fuel tank breather pipe and I need to drop it a few inches to gain access.

 

Thanks for the pointers.

Neil

[njc]

Hi Chaps,

 

I eventually got around to looking into the fault and I think it is fuel related and not electrical.

 

I ran the engine until warm. (Starts fine). When fully warm it starts to struggle at tick over then eventually stops.

 

As soon as this happened, I checked the spark into the dizzy cap and out to plug 1 and both have a good spark. I left the electronic ignition in but I think this all looks good. Rotar, coil and cap are fine. I am reasonably confident that the electrics check out fine and are not the cause of the problem.

 

I then got the car to start again and when I pull the throttle cable the engine dies almost straight away. This fault appears repeatable, engine must be warm and it cuts out as soon as throttle pressed or if left for a while dies on its own. Running ok at tick over then as soon as it needs more fuel as throttle butterflies open, it cuts out. I think its a fuel delivery problem. But is there anything I can do to check it out apart from buying new parts (expensive and may not find the problem straight away)

 

At start up my fuel pump (bosh) squeaks for a second until the system primes - is this normal?

I can hear fuel at the PRV being diverted to the tank.

Car starts normally and only cuts out only when warm.

 

I swapped the fuel tank with an ally one last year thinking it was rust in the fuel tank blocking the filter and fuel supply. The car lost power on a hot day and would not restart. Exactly the same symptoms as I have now.

 

The way the engine runs and then cuts out when I blip the throttle makes me believe it is a metering problem or the fuel to the MU pressure is too low.

 

What can I do to get this sorted? I want the car on the road and MOTed by May. IS it worth getting hold of a dial and plumbing to check pump and PRV pressure? I guess if this is between 100-110 PSI then it is most like MU control.

 

Any advice/knowledge appreciated!

 

Many thanks

Neil

[B Fitzpatrick]

Hi Neil,

try another coil as an easy elimination. Do you need a special coil with the electronic ignition.

 

Roger

 

 

Hi Neil

 

I could have written that script almost 18 months ago - as I say I'm with Roger on this one, if you have only checked the existing coil - no good, for a couple of quid source a new coil thats compatible with your electronic ignition - so about £30 - £35 (I'm converting from Euro) and 10 - 15 minutes work and you could be sorted, in the words of another esteemed Forum contributor "ask me how I know"

 

The next thing you need to know is how to use the search facility - so trick around with that and you will get a whole lot more information

 

Regards

Edited April 4, 2012 by B Fitzpatrick

[Guest ntc]

Favourite would be the coil , try it with the fuel cap open

[John390]

I agree with the coil problem, it happened to me. New coil then no problems. If not, make sure you have a full tank of fuel as if you are low the warm fuel returning from the tank evapourates and then the engine dies!

 

Cheers John

[njc]

Ok, I have a spare coil to try.

 

The one fitted is for a ballasted system. I still can't see how this is the problem since if I connect the lead from plug 1 to a spare spark plug earthed on the battery -ve and crank the engine there is a good solid spark all the time. Surely if the coil was suspect this spark would be intermittent or weak/non-existent?

 

I'll try it and see if this works (fantastic if it does!) but I'm not convinced its electrics. How would the coil cause the engine to cut out when I blip the throttle when the engine is ticking over?

 

Neil

Edited April 4, 2012 by njc

[peejay4A]

I would eliminate the electrics by substituting the coil and going back to points.

 

If that doesn't work then you might have fuel vaporisation problems. My usual question is do you have stainless braided injector leads?

 

(null)

[njc]

Ok, I'll give it a try and swap coil then elec ignition.

 

At least it will be an easy and cheap test

 

I'll try to report back tomorrow!

Neil

[DIYBOSSCAT]

Neil, you mention that you have electronic ignition in the distributor, are you sure its for a ballasted system. I'm running a simonbbc electronic ignition and that states it has to be a non-ballasted system with a minimum resistance of 1.5 ohms between the + and - terminals with no other wires connected.

Yes you have a good spark when cold, is it breaking down when hot?

 

hope this helps.

 

Vince.

[njc]

Elec Ignition is for a balasted system as is the coil. Its an Aldon Ignitor. I think it works when hot since I can see a good spark if I connect it to a plug with the plug grounded to the battery -ve.

 

I'll change the coil and see what it does

 

Neil

[Peter Cobbold]

Neil. You found that "When fully warm it starts to struggle at tick over then eventually stops.

As soon as this happened, I checked the spark into the dizzy cap and out to plug 1 and both have a good spark."

That indicates to me a fuel problem.

Tony suggested adding fresh fuel to dilute the stale stuff - I agree. Stale fuel that has lost volatiles will ignite slower, so despite the spark timing being by the book, will heat up the exhaust valve. When the valve gets too hot after several minutes' tickover it could lead to a second flame front and rough running, and failure to respond to the throttle.

Peter

[Dave Dawson]

Hi neil

I had as simliar fault on my 68 tr5 were it would start to cut out when warm, the car would splutter about until speed had dropped to 30mph only then i could slowly feed the throttle in, any harder the engine would start to stall, the warmer the weather the worst it became

I changed all igniton parts the mu had done only 1k the fuel pressure was 95 psi at idle in desperation i bought a full prestige pump and filter kit. On Good friday last year i drained the tank and removed the Bosch pump from the rear wheel arch only then did i noticed that the pump had rotated on it bracket and the positive terminal was touching the bracket,were there was green corrosion.I checked the resistance to earth at 1.5 ohms. after adusting the bracket the resistance increased to 10 ohms(the new pump read 11) this would indicate that pump electical feed was shorting out also the ignition switch contacts showed stress. I re installed the original pump and have now covered 4k miles with out the fault re-occuring. I would recommend connecting a Volt -meter directly to the pump so you can monitor the supply when the fault occurs.

[njc]

Thanks for the tip Dave! This sounds like what I have experienced last summer when it cut out on me on a hot day run to the shops. I left it to cool and then it ran normally.

 

Peter - re Fuel. It did this to me last year on a tank of fresh fuel. I could add some more but I'm trying to drain it down to do some remedial work on the fuel tank breather connection.

 

I will try a spare coil (one on order) but I am still tending to think it is MU, PRV or pump. I did think further, the pump is fitted with a relay and separate feed and that relay is just about man enough for the job but it does get warm. Perhaps I am getting volt drop. However this would not explain the problem only when warm. It starts fine from cold.

 

I'll report back after I swap the coil and see if that sorts it!

 

Neil

[njc]

Hi Folks,

 

Today I swapped the coil but the engine cut out problem still persisted. I then went to change the rotor arm for one of the red ones from Distributor Doctor. While I was at it I also took the opportunity to put some 3 in 1 oil down under the electronic ignition base plate. IT felt a bit stiff when twisting the base plate manually. It seems to be a bit better but I'm still not convinced it's fixed the problem. If I blip the throttle it dies, but not quite as bad as before! If I slowly increase the revs then the engine stays running and pulls fine.

 

It's as if there is a fuel delivery problem. Mixture or fuel supply problem perhaps? It then started to rain so I abandoned work. I am replacing the wiring from the relay (in the boot) to the Bosch fuel pump. It has got hot and melted the insulation on the spade connectors (indicating a resistance and a volt drop). Perhaps the pump isn't giving the fuel delivery I need? I've already uprated the wiring from the engine bay to the boot.

 

Any ideas?

 

All that is left on the electrical side is the Ignitor elec. ingnition. I'll try points when I get a better weather day!

 

Question - if I take the cap off the MU is this a problem? I was wondering if the internals - springs etc. need lubricating?

 

Question - is there a filter in the PRV - is this easy to clean?

[marki]

hi.

 

just had a similar problem would not start when warm. turned out to be nothing more than the fuel pump inertia switch, fine when cold cuts out ounce warm. good luck .

 

mark.

[Jersey Royal]

Hi Folks,

 

It's as if there is a fuel delivery problem. Mixture or fuel supply problem perhaps? It then started to rain so I abandoned work. I am replacing the wiring from the relay (in the boot) to the Bosch fuel pump. It has got hot and melted the insulation on the spade connectors (indicating a resistance and a volt drop). Perhaps the pump isn't giving the fuel delivery I need? I've already uprated the wiring from the engine bay to the boot.

 

Any ideas?

 

All that is left on the electrical side is the Ignitor elec. ingnition. I'll try points when I get a better weather day!

 

Question - if I take the cap off the MU is this a problem? I was wondering if the internals - springs etc. need lubricating?

 

Question - is there a filter in the PRV - is this easy to clean?

 

 

 

Neil,

 

Have you replaced the wiring as a result of the melted connection?

and the problem persists?

 

How have you wired it?

 

There is a small filter in the Prv, there was athread on this recently. You will need to clamp the fuel pipe

and undo the end fittting (with the tube on) and then take off the t part of the fitting the filter is in there.

If you dont have a manual look at the Mos or Rimmers website for a pictorial of it.

 

There is also a similar filter in the Mu, its just inside the body where the main fuel enters. To clean rinse

in petrol.

 

I havent re read this thread but you have checked that you have full flow fuel from the tank to your pre filter and thefilter is clean and that all

pipework is unkinked.

 

Good Hunting

 

Guy

 

 

I dont think you will gain anything by taking of the cone, there are no moving parts. Leave that well alone.

[john.r.davies]

Check the vacuum line to the Metering unit.

If it is leaking - eg cracked in storgae - then the unit will be setting the fuelling rich, so that when the engine is warmed up the fully vapourised fuel takes the mixture impossibly rich.

With the same intent, check the choke control at the M/u - is it fully back, ie closed?

 

John