2.25L Engine runs bad when warm

**Nighthawk** · 9th November 2013, 06:39 PM

Engine starts and performs well during warm-up period. weber performs well in that time,

It gets worse as it warms to operating temp, and becomes unreliable and temperamental. First symptom will be it bogs down and gives a kangaroo hop when on full throttle. When I back off the accelerator it corrects itself and runs somewhat smoothly. Coasting and slow accelerating somewhat ok.

It becomes worse as time goes on, it seems to get hot although the temp gauge stays around the middle of the gauge.

Symptoms vary slightly between the Zenith and Weber carbs but ultimately it either stalls and becomes un-driveable or with the weber it just runs erratic and bogs down as if there is fuel starvation., Problems only when hot after 10-15 mins driving.

is this a classic case of VAPOUR LOCK?

Ive done:
Cleaned carbs, fuel tank drained, compressed air up the fuel lines, fuel cap considered and drilled hole in the 2nd skin to aide breathing, changed fuel pump, took away the inline fuel filter for testing purposes, checked float levels, using 98 octane fuel, timing adjusted, swapped out the distributors and coils,(one electronic) renewed and re-routed fuel line from pump. checked for gasket/manifold leakages. new spark plugs fitted. checked carb linkages, tried different idle mixtures, check timing again.

It starts and runs strongly until it gets to hot operating temp and then runs poorly and eventually stalls and wont start with the Zenith. Weber is more forgiving.

Any insights and remedies welcome. Was thinking maybe the next step is electric fuel pump.

What are the right specs ie, PSI value?, GPH or Litres / per minute flow rate that would suit this application? Do I need a regulator with these low pressure pumps. The free flow rate of the Carter pumps are substantially more than the Facet type pumps. Is there ones to avoid.

Sorry for the length of the post but its been a lengthy problem NH.

**wrinklearthur** · 9th November 2013, 07:44 PM

Go back and replace that coil with another known good 12 volt one, it might be breaking down as the coil warms up and temporarily run the coil power feed from a direct source, to eliminate any dodgy connections like a crook ignition switch contact.

Check the earthing wire is in good condition between the moving points plate and the body of the distributor.

A engine does use less petrol as it warms up, so that should rule out any fuel supply deficiency.
.

**JDNSW** · 9th November 2013, 08:45 PM

I agree that it sounds a bit like an electrical problem, and the coil would be the prime suspect. But it could also be the capacitor in the distributor, or an electrical connection somewhere in the ignition.

You could rule out the fuel supply by temporarily teeing a pressure gauge in just before the carburetter and checking pressure. One slight possibility is that it is fitted with a diesel fuel pump that operates at higher pressure. This could be causing flooding that does not affect the engine when cold, where a richer mixture just means you push the choke in earlier.

Another thing to check, although the symptomms do not match exactly - assuming the crankcase PCV is fitted, disconnect it (and block the hoses) and see if that fixes it. A split diaphragm will cause all sorts of problems. (Do not just remove the PCV system - either leave it intact or fit the earlier open vented filler and rocker cover vent - an unventilated engine is a short lived engine.)

John

**bee utey** · 9th November 2013, 10:27 PM

If your sump contains petrol from a stuffed pump it will take quite some time before it all evaporates via the breather system. The hotter it is the richer it runs. Sniff the filler cap of the warm engine and see if you smell petrol. Draining and refilling the oil is best if this is indeed the case.

**Nighthawk** · 9th November 2013, 11:26 PM

Originally Posted by wrinklearthur

Go back and replace that coil with another known good 12 volt one, it might be breaking down as the coil warms up and temporarily run the coil power feed from a direct source, to eliminate any dodgy connections like a crook ignition switch contact.

Check the earthing wire is in good condition between the moving points plate and the body of the distributor.

A engine does use less petrol as it warms up, so that should rule out any fuel supply deficiency.
.

Thanks Arthur, Ive got a simonbbc electronic distributor kit which has its own high energy coil and I have a points distributor and its own Bosch SU12 coil. Changed both systems and have the same symptoms. By the way I notice no difference between the 2. In fact I think the advance is better on the original points distributor.

I haven't bypassed the ign switch but that is worth a try. The switch is old and worn no doubt. Ive had this problem since ive owned it come to think of it. Just haven't used it much in warmer months. NH.

**Nighthawk** · 9th November 2013, 11:33 PM

Originally Posted by bee utey

If your sump contains petrol from a stuffed pump it will take quite some time before it all evaporates via the breather system. The hotter it is the richer it runs. Sniff the filler cap of the warm engine and see if you smell petrol. Draining and refilling the oil is best if this is indeed the case.

Thanks Bee Utey, ill change the oil but I think its a long shot. The oil looks and smells robust as it usually is. Has a honey glow to it. The zenith carb dosent bog down and carry on but rather starts sputtering a bit and eventually stalls. Hard to start. Weber starts alright but loses power momentarily on take-off but recovers when revving a bit. Cant help thinking its a fuel delivery prob. Got an Allmakes mech pump on and the quality Im unsure of.

if I hook up an inline fuel pump what sort of pressure should I see. Or just do a direct pressure test? Cheers

**Nighthawk** · 9th November 2013, 11:38 PM

Originally Posted by JDNSW

I agree that it sounds a bit like an electrical problem, and the coil would be the prime suspect. But it could also be the capacitor in the distributor, or an electrical connection somewhere in the ignition.

You could rule out the fuel supply by temporarily teeing a pressure gauge in just before the carburetter and checking pressure. One slight possibility is that it is fitted with a diesel fuel pump that operates at higher pressure. This could be causing flooding that does not affect the engine when cold, where a richer mixture just means you push the choke in earlier.

Another thing to check, although the symptomms do not match exactly - assuming the crankcase PCV is fitted, disconnect it (and block the hoses) and see if that fixes it. A split diaphragm will cause all sorts of problems. (Do not just remove the PCV system - either leave it intact or fit the earlier open vented filler and rocker cover vent - an unventilated engine is a short lived engine.)

John

The engine has a cap on rocker cover and hose to air cleaner breather and open vented breather. I need to check fuel pump pressure. Ill get a gauge from somewhere and do it. What psi reading should I expect?

**wrinklearthur** · 10th November 2013, 02:27 AM

Originally Posted by Nighthawk

Thanks Arthur, Ive got a simonbbc electronic distributor kit which has its own high energy coil and I have a points distributor and its own Bosch SU12 coil. Changed both systems and have the same symptoms. By the way I notice no difference between the 2. In fact I think the advance is better on the original points distributor.

I haven't bypassed the ign switch but that is worth a try. The switch is old and worn no doubt. Ive had this problem since ive owned it come to think of it. Just haven't used it much in warmer months. NH.

Ref; https://sites.google.com/site/fifers...electronic-kit

"The earth wire is required to provide a good solid ground to the module.
You may get intermittent poor running if it is not fitted ."

"When it is fitted , note the clearance between the cut off peg and the new pickup ."

"Refit the baseplate and connect the other end of the original braided earth wire under the baseplate clamp screw .
Put the new Electronic wires and rubber sleeve through the distributor body ."

"It is recommended by SIMONBBC that you DO NOT USE A BALLASTED COIL but SHOULD USE A STRAIGHT 12V COIL . THIS MIGHT ONLY MEAN THAT IT REQUIRES A CONSTANT 12 VOLT SUPPLY "

.

**JDNSW** · 10th November 2013, 06:01 AM

Originally Posted by Nighthawk

The engine has a cap on rocker cover and hose to air cleaner breather and open vented breather. I need to check fuel pump pressure. Ill get a gauge from somewhere and do it. What psi reading should I expect?

I presume by "open vented breather" you mean the old pre-emissions filler pipe and cap - it should have a sealed filler pipe with a pipe and hose to a PCV on a bracket next to the carburetter hooked into a fitting just below the carburetter.

I can't find a reference to the fuel pressure, but it should be no more than about 3psi.

A further possible cause is too high a setting for float level, or any other carburetter problem that results in excessively rich mixture - with the Zenith this can commonly be that warping of the top plate results in fuel leakage past the O-ring or gasket; this can be remedied by lapping both surfaces flat. Having the problem with two carburetters makes this unlikely, but if no other problems can be found, it is always possible both have a similar problem.

John

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