Help. Help fuel injecrion problem I think!

[bpappas]

I have a 1973 914 with the L-Jetronic fuel injection. The car when climbing hills will stall, stop, and after waiting a few minutes fire up like nothing happened. I think it is temp related. The problem seems to happen after a long run up a hill. I live at about 5000 ft and the passes I am climbing are about 6000 ft. This seems to be pronouced at temps 50 F and above. I have moved the fuel pump up front under the tank so I don't think it is vapor-lock. It there anything to check? How can I test the temp sensor for the Fuel Injection to make sure it isn't the problem. Any thoughts would be helpful.


Perplexed in Porsche land

[Dave at Pelican Parts]

L-jet was not used until the 1974 model year. Make certain which system your car has; they are somewhat different. If your car has a silver hand-grenade thingie on the right side of the engine bay with one hose and four wires, it's D-jet. If it has the air cleaner on the left side of the engine bay with an air flow meter on the side of it (with a quarter-circle bump-out on the side of that) with one wire bundle plugged into it, it's L-jet.

For D-jet, see Brad's '70 914 2.0L . L-jet info can be found on Welcome to type2.com! ; the late Buses used L-jet EFI as well.

Actually, the L-jet temp sender is similar to the D-jet one; it's an NTC thermistor with one wire connection. You measure the resistance between that one wire and the cylinder head (or any other ground). It will be higher when cold, on the order of 1000-3000 ohms when very cold, and lower when warm, on the order of 100 ohms or less when the engine is at operating temp.

--DD

[bpappas]

Thanks Dave,

It's an L-Jetronic. As you can see the car has been messed with. Let me ask you this, how critical is having the proper fuel pump. The pump on there is aftermarket. I wonder if the car is vapor locking after all because it is running a small fuel pump that some ding a ling put in. Everything else sems to work to well. The car starts in cold (10F - 5F) very well. And on the flat it works well, it is just well it heats up and is climbing it will stall. Let it sit a while it will fine up fine.

Thanks for the help


BP

[Greenguy]

Not that this is the only issue that will cause the problem that you speak of, but I chased the same problem for about 4 months. Several on this board had mentioned the CHT sensor as the culprit but because of the thought of pulling threads out of the head I was reluctant to replace it thinking the whole time that it was something else. I finally resigned to the fact that it might be the CHT sensor and dove in and replaced....took about an hour, no problems what so ever. A picture of the old sensor follows.

Greg

[bpappas]

To Greenguy,

Thanks, I having been thinking about that too. Where did you get your sensor and how much did it cost?

BP

[Greenguy]

Got it for our host (Pelican)...it was in the 15 dollar range

[Dave at Pelican Parts]

As long as the pump can deliver the pressure and the volume required, it's fine. Assuming the plumbing has been made to work and doesn't leak.

--DD

[bpappas]

Thanks veryone. Changed out the CHT. A bit of a hassle to get to but well worth it. The old one was broke and was measuring an open, so it wasn't telling the fuel injection what it need to know. I won't know completely if it solved the problem until it warms up around here, but the car feels stronger and that tells me that mixture is more to normal.

Thanks again

BP

[Tobra]

L jet is air flow metered. If there are ANY air leaks on the intake side, it can allow unmetered air in and lead to lean condition> hot motor.

Does it always overheat, or only when going up hill..