Injected Manta won't run when hot..

[moodoo]

Hi all...am back again...thanks for sorting my previous problem out..
...So finally got to take the car on a long run, and discovered she has another problem! (Its an A-series manta, fitted with LE jetronic).

Seems like it won't stay running when it's hot. Drove for maybe 90mins on Saturday on open roads without problem, but as soon as I had to stop-start in traffic a couple of times, she started to splutter and die. Parked up for 10-15 minutes, and she went OK again for a few miles, before spluttering to a halt again. Repeat until destination is reached...

Replicated the problem in the garage a couple of times since. Leave the car idling in the garage for 20-25 minutes, long enough to get her 'hot' (She never actually overheats, gauge never beyond halfway), and slowly, slowly, slowly, the idle speed will drop and she will eventually die completely. She then won't restart unless its left for a few minutes.

First thought is the coil or the ignition amp? I'm pretty new to all of this, and don't really know where to start on this. I can bring the car somewhere to get her looked at, but would rather try to sort it out if I can, at least I might learn something...

Thanks in advance...

[newman27]

I battled this problem for some time and found it to be fuel starvation or vapor lock. I used a two part solution for my GT:

- Move your fuel lines away from the hotter parts of the engine and move your fuel filter to a cooler area with good airflow. I went with the fuel lines being routed along the firewall over the top of the valve cover and used ties to keep it "suspended" so as not to be touching any hot engine parts.

- The second part of my solution may not apply to you but I found my Hot Spark electronic ignition was acting up at high temps. I switched to a true Pertronix.

Since doing these two things I have been stuck in a lot of stop and go traffic on very hot 95+ degree days with no fuel starvation problems.

HTH,

Matt

P.S. I see you have fuel injection so maybe these tips don't apply but I thought I would mention them just in case.

[tomking]

I dont think it is the coil as it would just cut out and die. Plus if it was the coil you should see it reflected in the tachometer. I am not that experienced with fuel injection so can offer no help.

[wrench459]

Back in the late 70's Datsun FI units had heat shields,plastic spacers and hair dryers. All in the effort to cool down the fuel supply.
Before you start pulling your hair out..Try another brand of petrol. It might help then again maybe not but at least it'll give you a clue as to what might be happening.

Whats the fuel pressure when the old girl acts up?

[dallasmanta]

The Manta engine bay is well laid out and engine heat is not usually an issue for fuel lines. Well what you have described sounds like the engine is fuel starved when hot. This failure is symptomatic of a duel fuel relay failing when it gets hot. The fact that you can shut the car off allowing the relay contacts to cool down and then starting again till the contacts get hot and fail again.

This relay is the same as in a type 3 VW FI system. If you cant find the relay, you can use the following to make the unit servicable again. carefully remove the metal housing from the dual relay and use a 1000 grit wet/dry sand paper and clean the contacts/ points you will see when the housing cover is off. Use care not to spread the point beyond what you see when you first inspect the contacts. once the contacts are filed clean use an electrical parts cleaner spray give it a final cleaning. Now re-assemble the relay and install.

Test to see if the car will keep running when hot. I always keep a spare dual relay in the car just in case. This is an electrical part and will fail over time. If this fixes the problem buy an new one and install pull the used one and keep as a spare. Part number is stamped on the metal cover to the relay.

IF this does not fix the problem then there are other question for possible solutions. Ron

[moodoo]

Thanks...
Yes, it seems almost like a hot fuel problem, but feeling the fuel pump, filter and line going back to the tank, and they are all cold. Pump and filter are mounted underneath the floor, under the rear seat area.

As I have LE, I think I only have a single relay, not a dual one, but the theory is still sound, so cleaning the contacts is a good idea. Looking here: FI Conversion,
its pin 87b for the fuel pump. At least it's an easy one to try. Thanks!

[Nathan Acree]

I would check that your fuel pressure is not dropping after running for a while- could be the pump just can't make pressure after a while- fuel sock or filter gets clogged after running or the fuel pressure regulator is not functioning properly.

Hope this helps,

Nathan Acree
Albuquerque New Mexico

[wrench459]

Without opening up the relay can. You could check the voltage drop from pin 30 to 87 and 87b.

[moodoo]

I need to get a fuel pressure gauge assembly sorted out.

In terms of the relay, since I don't have a dual relay, all I could do was clean the pins on the relay (Lucas FDB501), but made no difference.

Wrench459 - Sorry for being a newbie, but what should I be seeing between plug pins 30 and 87/87b? Do you mean to check the volts across the plug, or the resistance across the relay?

[dallasmanta]

I am including a picture of the duel relay that is stock on the Manta. does the lucas unit look anything like this unit?

It might help us to see how your setup looks like under the hood. Your setup sounds non stock.

Do you have an inline fuse for the fuel pump similar to the factory set up coming out on the side of the fuse box. If so check this fuse as it will need to be cleaned and contacts checked. This Fuse over time will build up resistance and will get hot and my not be giving enough current to the fuel pump. Hot fuse means high resistance means the fuel pump will not run at full speed thus causing lower fuel pressure.

I am sure from the earlier post on the temp sensor you did check the air box flap to insure that it moves freely with no restrictions.

Other reasons for low fuel pressure out side of crimped lines or leaking lines, Clogged fuel filter by the pump. clogged filter sock on the in tank pick up. Fuel pump worn out ( makes loud noise when hot ) Fuel pressure regulator failure. Clogged fuel injectors that will not fully close.

I still think your issue is electrical. Opel ground wires are often at fault.

Ron

[wrench459]

Originally Posted by moodoo I need to get a fuel pressure gauge assembly sorted out. ... but what should I be seeing between plug pins 30 and 87/87b? Do you mean to check the volts across the plug, or the resistance across the relay?

Pin 30 of the relay should be B+(battery voltage) pin 87 or 87b should be the load(fuel pump) going to ground.

With an DVM leads back probed into 30 and 87/87b with the key off you'll see approx. battery voltage. With the motor running relay points closed you'll get the voltage drop across the contacts.
oophs it depends on if the relay is wired normaly open or closed.

If your fuel pump relay goes bad when on a road trip..remember you can jump out pins 30 and 87 on MOST fi car's and make it home.

[Gary]

Originally Posted by dallasmanta I am including a picture of the duel relay that is stock on the Manta. does the lucas unit look anything like this unit?

Don't forget that he has the "LE" Jetronic not the "L" that is stock in the '75 Manta.

Two manuals on the L-Jetronic are here:

L-Jetronic Manual

VW L-Jetronic workshop manual

[moodoo]

Originally Posted by dallasmanta I am including a picture of the duel relay that is stock on the Manta. does the lucas unit look anything like this unit? It might help us to see how your setup looks like under the hood. Your setup sounds non stock. Do you have an inline fuse for the fuel pump similar to the factory set up coming out on the side of the fuse box. I am sure from the earlier post on the temp sensor you did check the air box flap to insure that it moves freely with no restrictions. Other reasons for low fuel pressure out side of crimped lines or leaking lines, Clogged fuel filter by the pump. clogged filter sock on the in tank pick up. Fuel pump worn out ( makes loud noise when hot ) Fuel pressure regulator failure. Clogged fuel injectors that will not fully close. I still think your issue is electrical. Opel ground wires are often at fault. Ron

No, LE has a single relay, as per LE diagram here:
FI Conversion
I think the LE on my car is from a GT/E Manta B.

Inline fuse...i guess there must be one somewhere, will have a look.

Air box flap is fine, you're right, I had checked that during the coolant sensor troubleshooting...!

Fuel filter is new...can't vouch for the sock in the tank though. Leaving her to idle in the garage, fuel pump doesn't even get hot before the car dies.

Will check various grounds again, had also checked them when I was having my temp sensor problem. I am going to get an ignition amp and a relay, and try those. No harm to have spares in any case, and they're pretty cheap.

Originally Posted by wrench459 Pin 30 of the relay should be B+(battery voltage) pin 87 or 87b should be the load(fuel pump) going to ground. If your fuel pump relay goes bad when on a road trip..remember you can jump out pins 30 and 87 on MOST fi car's and make it home.

Thanks for that, good to know!

Originally Posted by Gary Don't forget that he has the "LE" Jetronic not the "L" that is stock in the '75 Manta. Two manuals on the L-Jetronic are here: L-Jetronic Manual VW L-Jetronic workshop manual

Thanks for the links, I had found those manuals when I was troubleshooting before, they were a great help, as was a link to a Porsche L-Jetronic manual I found on here somewhere too.

Thanks to all for advice and tips...

[Gary]

Originally Posted by moodoo I need to get a fuel pressure gauge assembly sorted out.

That would go a long was with helping to diagnose problems. I have one that I am planning to permanently mount in my Senator (someday).

[RallyBob]

Originally Posted by Gary That would go a long was with helping to diagnose problems. I have one that I am planning to permanently mount in my Senator (someday).

Under the hood would be good place Gary...nothing like a 45 psi fuel leak inside the car to ruin your day!

[dallasmanta]

Three questions on the LE systems. Do you have a O2 sensor in your set up ? Second do you have the factory electronic ignition and is it Lucas , Bosch? OR do you have a petronics type ignition trigger?

Test O2 sensor to make sure it is not making the mixture too lean and thus causing RPM to go below 400 as the ECU will kill the fuel to the FI system. If this checks good.

Test Ignition for spark when the car dies. Crank engine and test for spark at the plug. No spark will cause the ECU on the LE system to shutdown fuel to the system.

Lucas ignition module is a well known failure point when it gets hot. My MGB has not died since I replaced the Lucas one with Petronics.

That is all I have for the LE system. Ron

[moodoo]

Thanks a lot Ron.

No, there's no O2 sensor in the system.

Pulling plugs out and cranking, there is still spark, whether its as strong looking as when the car is cold I'm not sure. I'll need to test again, was in a bit of a hurry when I was doing this before.

I'm not sure what a Petronics is? I've got a hall-effect distributor, a Siemens ignition amp, and a Delco coil. I believe all this is standard Manta B GT/e stuff. I've ordered another ignition amp, and a fuel pump relay, so will swap these out when they arrive to test.

[dallasmanta]

The ignition amp is the part I was referring to in the earlier post.

Ignitor III

is what we use to convert from points and condenser to electronic ignition here. This unit eliminates the failures with a mechanical point system and the need to constantly clean and reset them. This unit is simple replaces the points and will hold settings till the cows come home all for under a hundred dollars..

Good luck with the part swap.. Ron