SPF GT40 MK1 - roush 427IR - Stalled

Hello,

We have recently imported in Europe a GT40 MK1 with a Roush 427 IR (8 stack fuel injection system) - 560 HP. The car has only 200 Miles on the clock.

The car is working fine, engine starts first try, pulls strong as you can expect from a 560 HP unit, it is working like it should.

Everything is fine until the engine gets warm and then if we are caught in a traffic jam, or even riding at low speed in town and stopping frequently at lights, the car will start to work bad and finally stalls. Then it is impossible to start it again. We had to trail it twice, let it get cold and then it started again.

We have checked what we could on the engine itself and injection system, but everything seems to work fine. It seems the headers are very close to the starter and might cause some troubles once the engine is warm but it does not explain the stall issue.

Any input would be much appreciated.

Eric
 
SPF GT40 MK1 - roush 427IR - Stall issue

Hello,

We have recently imported in Europe a GT40 MK1 with a Roush 427 IR (8 stack fuel injection system) - 560 HP. The car has only 200 Miles on the clock.

The car is working fine, engine starts first try, pulls strong as you can expect from a 560 HP unit, it is working like it should.

Everything is fine until the engine gets warm and then if we are caught in a traffic jam, or even riding at low speed in town and stopping frequently at lights, the car will start to work bad and finally stalls. Then it is impossible to start it again. We had to trail it twice, let it get cold and then it started again.

We have checked what we could on the engine itself and injection system, but everything seems to work fine. It seems the headers are very close to the starter and might cause some troubles once the engine is warm but it does not explain the stall issue.

Any input would be much appreciated.

Eric
 

Seymour Snerd

Lifetime Supporter
Everything is fine until the engine gets warm and then if we are caught in a traffic jam, or even riding at low speed in town and stopping frequently at lights, the car will start to work bad and finally stalls.

One common heat-triggered problem is so-called "vapor lock" in the fuel system caused by some part of the fuel system heating to the point where fuel vaporizes and prevents efficient pumping. A direct check on that would be to temporarily mount a fuel pressure gauge in the fuel system and see if it drops when the engine warms up and starts misbehaving.

Good basic article is here: http://en.wikipedia.org/wiki/Vapor_lock

An example of a low cost gauge set is this:

http://www.harborfreight.com/master-fuel-injection-pressure-test-kit-97706.html


Others familiar with the EFI system used on the Roush engine should be able to tell you how to connect it up.

A more general suggestion would be to find out who did the install and ask that person for suggestions.
 
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Chet Schwer

Lifetime Supporter
I think Alan is on the right track. Check and see if the fuel line to the injection is close any exhaust or engine heat especially if the injection is fed from the rear. If so, insulate the line with a heat sleeve and see if it helps. A picture might help us diagnose that kind of problem.
Chet
 

Ian Anderson

Lifetime Supporter
I would say not as described above.
I would look at the low pressure I.e. Tank to swirl pot as the place it is getting the vapour lock and you get a few minutes running as the swirl pot drains before it cuts out.

Possibly also the Debris /dirt from your fuel tanks blocking the lines and reducing flow

Check the fuel filters they are probably clogged.

I had a similar problem on my Dax with a much lower spec motor.

I also helped by installing 2 fans in the rear clip to help keep the sit moving.

Ian
 
Based on the limited information you provided I would agree with Alan. What kind of injection system are you running? Can you data log or provide a screen capture of what's going on when the car starts to hiccup. Also you might want to try to clear the problem with a blip of wide open throttle. It'll clear the vapor and introduce colder dense fuel

Also as Alan said you might want to install a gauge in the fuel system you can see through the rear window. I did this on mine and I can see fluctuations and deal with them if need be while moving.
 
Eric,
I think all the above suggestions are good and should be investigated. It is hard to imagine the amount of heat that builds up while the engine is just idling, especially with extra cubic inches!! I found out when my engine was tuned(EFI). My engine is a lot like yours. The person doing the tuning didnot know that my rear fans had to be turned on once the engine had warmed up. I have not yet installed a thermostat(air) that would automaticly trip the fans. So I have to tuirn them on manually for now. The fans I have are 2, 5" fans in the corners of the engine bay next to the firewall. I have them wired through an off delay relay from Waytech. This allows the fans to run for 3 minutes after the ignition switch is turned off(if they are on).
The heat build up actually bubbled the paint just above the highest exhaust tube. I have added some insulation just above the exhaust tubing to help block the heat.

IMAG0025-1.jpg

PC210051.jpg



Fortunately I plan to repaint the car in the spring.
What type of fuel lines are on your car. If they are hard lines you may want to think about using teflon coated lines. The rubber acts as a pretty good insulator.

Bill
 
Thank you very much for all your inputs. We will start by checking the fuel pressure in the fuel line and see if we have vapor lock problems.
 
Hello,

Well our mechanic has worked on trying to find the issue with our GT40.

The issue is that when the engine is hot, the car stalls and don't start again.

He has found that two of the spark plugs were dirty and blackened on cylinders 4 & 8 (the two opposites ones close to the firewall). What's more the temperature has been measured on all cylinders, and the one on cylinders #4 and #8 is half the one on the other cylinders.

He has done the following :
- Check compression : ok on all 8 cylinders
- Replace all spark plugs
- Swap injectors to control if one of them is faulty. Every single injector works fine.
- Check the ignition : everything works fine
- Check the fuel pressure : ok.

A that stage the problem is not solved. Our mechanic seem to get close to the end in terms of investigation of the problem.

We imagine that there might be a trouble with the injection electronic controler. But how do you get into that thing to chek if it works fine ?

Any other idea on solving that issue ?
 

Seymour Snerd

Lifetime Supporter
He has done the following :
- Check compression : ok on all 8 cylinders
- Replace all spark plugs
- Swap injectors to control if one of them is faulty. Every single injector works fine.
- Check the ignition : everything works fine
- Check the fuel pressure : ok.

A basic question: has your mechanic made the car fail himself?

I ask because, for example, "fuel pressure ok" while the car is in the shop is not useful information. My question would be "what is the fuel pressure while the car is hot and refusing to start"? This is easy to test: attach a pressure gauge, and drive the car until it fails; at that moment, look at the fuel pressure. If it is "ok" at that time, then you can say "fuel pressure ok". Otherwise, you don't know.

Similarly for other subsystems: you have to run the tests while the car is hot and refusing to start. To say "ignition works fine" you have to see a strong spark while the car is hot and refusing to start.

To be blunt: I'm concerned about your mechanic: if the car fails to run at all, why would he swap all 8 spark plugs? There's no possibility that all 8 spark plugs fail simultaneously and temporarily only when the car is hot.

Same comment about the injectors. Swapping them around makes no sense because there is no way for one injector to make the entire engine fail. Does your mechanic understand the problem you are trying to solve?

The black plugs is interesting, but possibly unrelated. Please verify again which cylinders it is: the two front cylinders? If so, that is cylinders 1 and 5, not 4 and 8.
 
If your engine is a Roush IR then it should have Accel electronics and it does have data logging either through the com cable and a lap top, 4 channel, or the O2 controller has 16 channel data logging including engine outputs for fuel pump so there has got to something in there to tell you whats going on.You have to have a switch to earth connected to AUX 1 on the O2 controller harness plug to access this.
Mike
 

Jack Houpe

GT40s Supporter
Its almost impossible to vapor lock an EFI system, the engine has a fuel pressure regulator then the fuel is constantly flowing. I am not familiar with Accel system but you might want to check to see if the manifold air temperature sensor has to much authority, which will lean the motor as air temps rise, to much authority will lean a great deal and just the opposite when air temps are cold it could be to rich.
 
A malfunctioning or an erroneous reading from the air temp sensor will not stop the engine in the Accel system. It SHOULD have a manifold suface temperature sensor, allthough this function can be disabled, and the ECM averages out the two to, in theory, calculate the port temp. Even if any sensor went down due to heat the Accel should not fail, it disables the O2correction and reverts to the tables as a drive home mode.
You should connect a lap top and see if any error codes are displayed, a big flashing light in the bottom right of the screen with an error code number.
Mike
 
I had once such thing on a old ford (4cill) a long long time ago...and in that case it was a bad transistor/condensator? or how you call such thing that was mounted next/on to the distributor/splitter thing...but I don't know were on your car such thing is :D

it can look like this>
article8552215.jpg


when cold all worked fine...when getting hot it the trouble begun...then nothing...but after a cool down all worked again :) maybe your lucky and have the same problem, a faulty electronic part.

Also it could be a faulty Bobine when getting hot...both are not expensive I think.
 
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Seymour Snerd

Lifetime Supporter
Ibut I don't know were on your car such thing is :D

Rene -- That's a condensor and being an electrolytic capacitor they are notorious for failing in a temperature-sensitive way. AFAIK they are found only on points-type distributors so I think it's unlikely that is Eric's problem. I'm hoping Eric does not have an "electronic hardware failure" problem because it's likely to be expensive to fix since all his electronics are in his EFI box. A loose wire would be nice problem to discover right about now....:uneasy:

Eric -- you're getting some good advice from the EFI (Electronic Fuel Injection) experts. You might want to take your car to someone who is familiar with programming and debugging those systems.

Mike, Jack -- does the "two cold cylinders" symptom make any sense to you? Any chance the Accell system thinks it's a V-6? :embarassed:
 
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can such car be plugged in into a laptop? if so maybe they can hang it on starting from cold and let the engine run till the fault appears also on screen and maybe then you can tell were it probably is?
 

Jack Houpe

GT40s Supporter
Rene -- That's a condensor and being an electrolytic capacitor they are notorious for failing in a temperature-sensitive way. AFAIK they are found only on points-type distributors so I think it's unlikely that is Eric's problem. I'm hoping Eric does not have an "electronic hardware failure" problem because it's likely to be expensive to fix since all his electronics are in his EFI box. A loose wire would be nice problem to discover right about now....:uneasy:

Eric -- you're getting some good advice from the EFI (Electronic Fuel Injection) experts. You might want to take your car to someone who is familiar with programming and debugging those systems.

Mike, Jack -- does the "two cold cylinders" symptom make any sense to you? Any chance the Accell system thinks it's a V-6? :embarassed:

Sounds like Mike has experience on accel system go with his advice. But on most other EFI systems that are not true sequential they fire batched ignition and fuel injectors. I think the Roush motor is a Windsor based motor with a firing order of 13726548 so batched would be 1-6, 3-5, 7-4, 2-8. With this order even if accel is batched it would not effect those two cylinders (4-8) without affecting the other two its batched to.

Check fuel pressure first, (I have a gauge in my fuel rail that I can see in my rear mirror), then if you have data logging read the stored file if there is one.
 
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