What might be the problem? Won't start when hot!

**Simon Kelly** · 07-05-04, 04:58 AM

Hi All

I have done a search, but can't find what I need.

Why won't my GTD40 start when hot?

I have had this problem ever since I bought the car and it is a tad inconvenient to say the least. Basically the chain of events are as follows.....

The car starts fine when cold, but when hot the starter motor didn't turn over properly - it sounded like a flat battery - whrrrrr........whrrrrr.................whrrr. If that makes sense!

So far I have done the following....

Upgraded all the earth leads on the car and made sure there are good earth points on the chassis.

Upgraded the starter motor to a high torque unit from Mark at MDA. It turns over now like a jet engine - much better! When hot it is a bit slower, but turns the engine over fine.

The engine bay gets really hot, but I have upgraded the water pump to an EWP electric pump and this works very well.

Car still won't start!

What should I look at now?

As I have said before, I am not a mechanic - I just about have "blonde" knowledge of how an engine works, however, I can follow instructions very well!

I have a standard GTD double fuel pump set-up and elderbrock performer head etc. Mallory electronic ignition. Carter carb.

I think it must be a fuel problem - is the heat soak of the engine evaporating the fuel before it gets to the carter carb? The engine turns over, but never sounds like it will fire.

If I wrapped the exhaust - would this help? Should I sheild the starter motor? Any other suggestions...HELP!

Thank you for any ideas you might have.

Simon kelly

JP · 07-05-04, 05:01 AM

Sounds like fuel evaporation to me Simon. I would contact Frank Catt, he's probably quite familiar with your problem.

I can't help because I'm just a frigging retard! [img]/ubbthreads/images/graemlins/grin.gif[/img]

Regards,

J.P

Malcolm · 07-05-04, 05:18 AM

If it is fuel evaporation, heat sheild wrapping the fuel pipe from where it is near the engine to the carb is worthwhile. I have done it on my car but this was to stop fuel evaporation at the Brighton Speed Trials when the car was sitting idling a lot and the fuel disappeared just when it was needed ie the start line! Now I get the wife to push the car 1/2 mile to the start line!

If you have already upgraded you starter motor to the MDA unit, a good unit so I am told, I can't think what else to say apart from check for good sparking, good fuel supply and delivery and correct timing.

Sorry if this is not much help.

Simon · 07-05-04, 07:29 AM

Simon,

I would guess everyone is right with their answers here. When I bought my car, the builder told me he had fitted two separate switches for the pumps instead of a right one on or left one on type switch. He told me he used to switch the pump off slightly before he got anywhere on a hot day so the fuel was drained from the carb and refilled with fresh, colder fuel on startup.
Also he fitted two polished ali "guards" either side of the engine (see pic, rhs shown) to cut down on the radiated heat from the manifolds.
Simon

Lynn · 07-05-04, 11:10 AM

If all else fails, you might want to consider a return type fuel pressure regulator. This might help take some of the heat out of the fuel system. This is more of an EFI type thing, but I thought it just might help.

Lynn

Howard Jones · 07-05-04, 12:37 PM

1. Does the engine turn over at the same speed when hot that it does when cooler or good morning cold? If engine cranking speed is a problem then heat shield the starter.

2. The next time you have it out on a warm day, run it until it is good and hot back there in the engine room. Turn it off and right away start it back up. Right away means seconds not mins. If it starts normal then turn it back off and wait a couple of mins to allow the fuel lines to heat soke. Now start it. Did the problem return?
If so heat buildup in the carb or fuel lines MAY be the problem. Do you have fuel in the fuel bowls? Check thru the float site plugs. Clear ones work real good for this. Or you can just have someone pump the acc. pumps and look down the carb. Be careful of the hot everything fuel issue.

3. No fuel could be, very hot engine room has evap. fuel in bowls, acc pumps on carb incorrect stroke/worn, fuel delivery issue with heat problem effecting fuel lines. Check this by pulling off fuel line to carb and just very quickly have other person turnon off pump switch. Fuel should appear, INTO A COFFEE CAN WITH A RAG IN IT TO PREVENT SPLASH, within 2-4 secs(my car,GTD) or the same time as your car when cold. Same heat fuel warning as above.

4. Fuel lines hot? wrap them. Carb hot? Hummm Shields under carb to seal off carb from below might help but the header heat fixes might be needed anyway.

5. None of the above? This also could be a heat related problem with the spark system. The distributor has electronic components inside. These can be subject to heat soke also but it is less likely. The best way to check this is to, when engine is hot and will not start, quickly remove dis. cap and blow on internal components with cool air, put back cap and start. Works OK now? Mag pickup or optic pick up could be going bad.

7. If your spark box is inside engine room then they are hard to do the quick cool down method of checking because all the components are inside the box. How close is it to the headers? Heat shield this too of move it farther away from the heat sorce. Swap with another one if you can get a lowner.

8. This could also be the coil. Same process when engine is hot and will not start, quickly cool down coil with damp cold rag, dry off, then start. OK now? Try different coil.

In the end you will want to shield starter, shield fuel lines, and apply jet hot to, or wrap headers anyway. All of which are good ideas.

I hope I have helped a little.

Hershal Byrd · 07-05-04, 01:42 PM

Simon,
You need to know if your engine is running hot or if the engine compartment is not able to expell all of the hot air. Go purchase a hand held lazer thermometer. They cost about $39 USD. This little devise will help you find the areas that are causing the heat build up. I use mine all the time to see if my cooling system is operating properly. You can detect areas under the clip that are getting the hottest including the starter. The headers put out a tremendous amount of heat and that heat can expand onto other componants. If your fuel pumps are near by then it is possible that they are obsorbing the heat from the headers. A good ceramic header coating will help but you may have to relocate your pumps if possible. There are places under the clip that can reach 500 degrees FHT. If your pumps are within 6" to 8" of the heat source then I would definetly move them. Also they sell fuel line insulation for the section that feeds the engine. One other thing is the lemans panel on the top of the rear clip. If it is a louvered one then it may not have enough louvers to allow the heat to escape. Take it off and use the thermometer to see if it relived any of the heat build up. I bet it does.
I hope all of these ideas from the forum are helping. Let us know what the results are.

Hersh [img]/ubbthreads/images/graemlins/smile.gif[/img]

**Simon Kelly** · 07-05-04, 02:16 PM

Thank you Guys!

I have a veritable shopping list of new things to try. Marvelous!

It always amazes me how willing people are to help and the knowledge you all hold - where would we be without the internet!

Again thank you - I will let you know how I get on.

Kind regards
Simon

Howard Jones · 07-05-04, 04:28 PM

Simon, Last thing. It is possible but unlikely that the set of contacts inside the key switch that supplies 12V to the coil ckt are going bad. What could happen is as the car runs that set of contacts begin to heat up or even burn slightly and after you turn the car off they remain in a marginal state until they cool down.
I only mention this as a kinda last thing it could be. It can be checked by measuring the voltage at the coil when you do a good morning start and then again when you have your problem. Pretty easy to eliminate. The voltage here should be the same each time if the battery remains contant.

That could also be another sorce for your problem, Battery voltage. Have a look at it just before you turn the key from run to start each time you start the car. Hot or cold. Batterys will act funny when they get very hot. where is it located? Think radiant heat.

Good luck

Kalun D · 07-05-04, 10:28 PM

Problem Diagnosis is a process of elimination.

Basically you need 3 things for an engine to run.

compression

ignition

fuel

First try to determine which of these 3 has the problem then move on to determining the exact cause.

In this case you can eliminate compression because it's a starting, not a running problem, and it's intermittent. Chances are it's fuel or fire.

To test ignition.

Take a small screwdriver and remove a plug wire at a plug, insert the screwdriver where it touches the metal contact inside and hold the screwdriver by the handle with the blade about 1/4 inch away from any metal ground. Preferably nothing with fuel in or nearby.

Make sure your hand and any part of your body is at least a couple inches away from the metal blade of the screwdriver. It's also safer if you don't let any other part of your body touch any metal on the car, thus eliminating the electrical path to ground.

(don't recommend this method for heart patients!)

Have someone crank the engine over and look for blue spark, increase the distance of the blade to ground from 1/4" up to 1/2". It should spark nice and blue up to a 1/2" gap. You can get faked out here if you see spark at 1/4", it's not enough to fire under compression. There are certain problems that cause a weak spark, so you need to know if there is no spark or a weak spark.

It's an invalid test to use a spark plug because the gap is too small. When the plug fires in the cylinder the compression of the fuel/air mix causes resistance to the spark jumping the gap, thus requiring a hot enough spark that will jump a 1/2" gap in ambient air.

For heart patients you can also purchase a cheap spark tester with adjustable gap for about $5.00.

Once you have determined you have spark you can move on to fuel. There are other ignition problems that can cause no start when you do have fire such as bad plug wires and spark timing but those are doubtful with the "only when hot" symptom.

To test fuel.

Look down the carb barrels and pump the gas all the way 2 or 3 times to see if the accelerator pumps are squirting each time. You should see a small stream of fuel squirting into the barrel. This most likely tells you there's fuel in the carbs but not necessarily that it's reaching the cylinders in the correct amount.

A better test is to take some carb cleaner or starter fluid and squirt a smallish amount down the carb primary barrels while trying to start the engine. If no fuel is the problem the engine will run briefly on the fluid your supplying.

(This type carb (I believe) has primary and secondary barrels, the 2 primaries open first then the secondaries on full throttle.)

++++++++

The "only when hot" symptom most likely points to a coil or ignitor failure if it's ignition and a vapor lock or evaporation problem if it's fuel.

Coil and ignitors are best tested by replacement, they have electrical tests for them but these aren't always conclusive and sometimes misleading. Also others suggesting cooling via water mist or pressurized air is correct.

Vapor lock is a condition where the fuel boils and the pressurized vapor blocks passage of the liquid fuel. The infra-red temp gun will be handy in this case to find hot spots.

Paul W · 07-05-04, 10:46 PM

Does the carter carb have manual or electronic choke setting ???
I used to have this very problem on an automatic choke carbed pinto.
It would run perfectly for hours and as soon as you stop at services (just for 2 mins)it won't restart unless you let it cool abit.
It turned out to be running slightly too lean when idling and was adjusted.
Are your spark plug deposits the right colour ???

**Simon Kelly** · 07-06-04, 04:06 AM

Hi All

Yet again - some excellent suggestions and described in such a way that I can follow the instructions perfectly!

I am going to start looking at it today and will keep you informed as to what I find.

Again thankyou all.
Simon

SpyderMike · 07-06-04, 12:39 PM

Your problem sounds like mine on my car - it is the starter in my car. When hot from driving it won't turn over or slowly like a flat battery. I let it cool down and it turns over fine.

Dave Bilyk · 07-06-04, 02:52 PM

Mike, if I have this right, this isn't Simons problem because he says his engine turns over fine when hot now he has upgraded the starter motor. Mine behaves the same as yours Mike, in fact it tends to turn slowly when hot and stop dead at first fire. The second time I turn the key it fires and runs. For the first few hundred miles I firmly believed it would fail to start when hot, but it never has so far. So there seem to be two issues here, ours involving the starter, and Simons involving something else which prevents fire.
My engine is just basic carburetor, a Holley, my fuel pumps are low down near sump level so they dont get too hot. At the carb, heat ensures that the fuel soon evaporates from the carb, then when I switch on there is much clicking of fuel pumps so I think the carb gets filled with cool fuel and there is no problem getting fire.
Not sure if this helps you Simon or helps anyone, but there it is.

SpyderMike · 07-06-04, 03:53 PM

I see what you are saying - I had a hard time waking up this morning and didn't read his post too well.

Howard Jones · 07-06-04, 06:28 PM

Dave I have a GTD and my car does the EXACT same thing. Its the starter motor we are using. The engine tightens up when it is hot. The starter motor gets heated up back there in the engine room and then it just doesn't have enough poop. Mine always seams to start though, and I suspect it's because I have a MSD 6AL and distributor in it. Lots of fire on the first crank.

I think this is common with the supplied GTD starters. The Mark Sibley adapter and gear starter is the solution as I see it. I will do this some day when I get some money not spoken for.

Mark Clapp · 07-06-04, 06:57 PM

On the slow starter issue, I've heard that increasing the ground cable to a thicker one, such as welder's cable (OO) can help. Maybe another thing to try. I get that with my car when hot. My auto electricians say that my Lucas starter is an industrial unit and is a low-torque type. They say it is working like it should and has never failed to start although it is slow when hot. Any other Lucas units out there?

**Simon Kelly** · 07-07-04, 05:19 AM

OK - An update....

Armed with a print out of everyone's thoughts on the subject, a friend of mine Neil, an excellent machanic, who is not frightened of the car and I, set to work. Frightened of the car? So many people shy away from doing anything to the car - its too specialist. ITS JUST A BIG V8 - for Gods sake!

We both agreed that we had solved the starter mo