Is this the dreaded 914 vapor lock?, Asking for your ideas and thoughts Options

[wonkipop]

Discovered the temp sensor in the RH head became disconnected.

(IMG:style_emoticons/default/beerchug.gif)

by the way thats great you have reported back art.
if someone else gets into a similar problem they can tick that off their list of probable cause. good on you.

[emerygt350]

Discovered the temp sensor in the RH head became disconnected.

(IMG:style_emoticons/default/beerchug.gif)

by the way thats great you have reported back art.
if someone else gets into a similar problem they can tick that off their list of probable cause. good on you.

And that was all it was?

[Artfrombama]

Discovered the temp sensor in the RH head became disconnected.

(IMG:style_emoticons/default/beerchug.gif)

by the way thats great you have reported back art.
if someone else gets into a similar problem they can tick that off their list of probable cause. good on you.

And that was all it was?

Yes, no one to blame but myself.
Spade terminal inside a plastic sleeve. Difficult area to get to, difficult terminals to connect properly.

[emerygt350]

Discovered the temp sensor in the RH head became disconnected.

(IMG:style_emoticons/default/beerchug.gif)

by the way thats great you have reported back art.
if someone else gets into a similar problem they can tick that off their list of probable cause. good on you.

And that was all it was?

Yes, no one to blame but myself.
Spade terminal inside a plastic sleeve. Difficult area to get to, difficult terminals to connect properly.

Well, thank goodness you found it.

[Artfrombama]

Discovered the temp sensor in the RH head became disconnected.

(IMG:style_emoticons/default/beerchug.gif)

by the way thats great you have reported back art.
if someone else gets into a similar problem they can tick that off their list of probable cause. good on you.

And that was all it was?

Yes, no one to blame but myself.
Spade terminal inside a plastic sleeve. Difficult area to get to, difficult terminals to connect properly.

Well, thank goodness you found it.

Yes, a pair of Webers were starting to look good!

[ClayPerrine]

Yes, a pair of Webers were starting to look good!

Please don't put webers on it. The stock injections is far better than webers, and modern EFI has them both beat hands down.

[JeffBowlsby]

The factory service bulletin to address fuel vapor lock issues:

https://bowlsby.net/914/Classic/zSB_1973-10-06_P213.pdf

[wonkipop]

Yes, a pair of Webers were starting to look good!

Please don't put webers on it. The stock injections is far better than webers, and modern EFI has them both beat hands down.

@ClayPerrine

art is still having problems with it.
got a PM. ran fine yesterday. so he buttoned it up after attending to temp sensor 2 plug.
but today problem is right back. fires then dies i believe. same problem.

art was asking for the full pin out test.
i know its not really there in the factory manual and i swear i have seen it posted here.
i cannot dig it up in my files. i have put it somewhere but now i cannot find it.

i sent him the link to the 912E L jet troubleshooting guide i had which jeff bowlsby has on his site.

he needs to test the EFI loom from AFM to ECU.

@JeffBowlsby
i don't believe art has a vapor lock problem.
its doing the same thing intermittently parked stone cold in his garage.
one day it runs. the next it doesn't. always the same symptom he had when it first popped up out on the highway. see his first post.

really feels like an intermittent electrical connection or component fault.

he has swapped out dual relays to test. etc.
he can give you the full list of things he has done.

its an interesting problem.
i figure clay perrine might have the insight to get to the bottom of it.

he has the link to the full set of factory manuals i sent to him.
so he can go back to fully testing his fuel system with both pressure and flow.
but i don't think its that.

[Artfrombama]

Yes, a pair of Webers were starting to look good!

Please don't put webers on it. The stock injections is far better than webers, and modern EFI has them both beat hands down.

@ClayPerrine

art is still having problems with it.
got a PM. ran fine yesterday. so he buttoned it up after attending to temp sensor 2 plug.
but today problem is right back. fires then dies i believe. same problem.

art was asking for the full pin out test.
i know its not really there in the factory manual and i swear i have seen it posted here.
i cannot dig it up in my files. i have put it somewhere but now i cannot find it.

i sent him the link to the 912E L jet troubleshooting guide i had which jeff bowlsby has on his site.

he needs to test the EFI loom from AFM to ECU.

@JeffBowlsby
i don't believe art has a vapor lock problem.
its doing the same thing intermittently parked stone cold in his garage.
one day it runs. the next it doesn't. always the same symptom he had when it first popped up out on the highway. see his first post.

really feels like an intermittent electrical connection or component fault.

he has swapped out dual relays to test. etc.
he can give you the full list of things he has done.

its an interesting problem.
i figure clay perrine might have the insight to get to the bottom of it.

he has the link to the full set of factory manuals i sent to him.
so he can go back to fully testing his fuel system with both pressure and flow.
but i don't think its that.

Non not a vapor lock problem, I thought the fuel pump was the problem because I was getting erratic fuel pressures. I have replaced the original (rebuilt) fuel pump with a replacement from the jungle site, replaced the fuel pressure regulator.
Occasionally I can hit the key and the car will start normally and idle great for a few seconds but most of the time the motor will crank, crank, crank and occasionally “hit”.

Even though the units are quite robust I’m starting to suspect the ECM.

Things I have checked;
Super white hot spark, plugs firing normally
Tried another (new) dual relay
Thermal switch II (In RS head)=14K ohms
12V power to injectors=yes
Good grounds=yes
Pulse from -coil to pin 1 on ECM-yes
Fuel pressure=yes
Fuel pump runs from AFM

A pin-out diagram would be helpful in eliminating broken wiring.

[Superhawk996]

The temp sensor in the head - TS2, commonly called cylinder head temp (CHT) sensor should not be 14k ohms at room temperature conditions.

Here is the plot of temp sensor resistance vs temperature


14k ohm from CHT is going to force a very rich cold start condition. During summer temps would be too rich to fire.

Are plugs wet and/or black soot covered immediately after trying to start the car?

[wonkipop]

CHT test for the L jet from factory manual.
tricky to measure given temp sensitivity.
but certainly not in range.

[ClayPerrine]

The L-Jet wiring is now more than 50 years old, and it lives in a harsh environment. Wiring of that vintage is now breaking from heat cycling and the insulation getting brittle. Based on what he has already done, I would suspect that there is an old wire in the harness that is going open circuit due to vibration.

The other alternative is just as bad. The 50 + year old ECU is failing intermittently due to vibration.

My suggestion would be to invest $455 in a new harness from Bowlsby.net. This eliminates old wiring as a possibility. If it doesn't fix it, I will be happy to send a different ECU. I have lots of them.

Clay

[JeffBowlsby]

A pin-out diagram would be helpful in eliminating broken wiring.

https://bowlsby.net/914/WiringHarnesses/doc...ECcode_1.8L.pdf

[ClayPerrine]

A pin-out diagram would be helpful in eliminating broken wiring.

One problem. If it is intermittent, it may not show up when testing the harness but show up when it is in use. I have seen harnesses that test good, but only have one strand left in a critical connection. Under load, they fail.

[Artfrombama]

The temp sensor in the head - TS2, commonly called cylinder head temp (CHT) sensor should not be 14k ohms at room temperature conditions.

Here is the plot of temp sensor resistance vs temperature


14k ohm from CHT is going to force a very rich cold start condition. During summer temps would be too rich to fire.

Are plugs wet and/or black soot covered immediately after trying to start the car?

@Superhawk996 Apologies, 1400 ohms, not 14K.
The plugs are black but dry.

[wonkipop]

@ArtfromBama

ah yeah, thats probably right for the cht. given its summer over there isn't it.


one of the things that can produce this problem is the harness connecting the AFM and the ECU. i feel the plug to the AFM is particularly vulnerable like all plugs. taking them on and off over the years to service car. removing air filter and replacing etc.

on an original wired car with original wired fuel pump if that pump signal doesn't get through it won't run. i think i have mentioned it before on this topic. i've done it, like a dunce, forgotten to replug in the AFM. it will fire (off the squirt it gets from the cold start injector) and then the pump will only continue to run on command from the AFM.

another thing to check is the TPS under the throttle body.
make sure its working. the tests are in the factory manual.
make sure its electrical connection is clean and good.
when the throttle is not open, the idle setting on that is sending a command to let the ECU know the car is in idle.
The TPS on the L jet is much simpler than the D jet.
its basically an idle setting. and a wide open throttle setting.
all inbetween is run off the AFM to the ECU.

i think mr. perrine is right. its likely to be that harness. its occasionally connecting.
sure sounds like its there.

[Artfrombama]

@ArtfromBama

ah yeah, thats probably right for the cht. given its summer over there isn't it.


one of the things that can produce this problem is the harness connecting the AFM and the ECU. i feel the plug to the AFM is particularly vulnerable like all plugs. taking them on and off over the years to service car. removing air filter and replacing etc.

on an original wired car with original wired fuel pump if that pump signal doesn't get through it won't run. i think i have mentioned it before on this topic. i've done it, like a dunce, forgotten to replug in the AFM. it will fire (off the squirt it gets from the cold start injector) and then the pump will only continue to run on command from the AFM.

another thing to check is the TPS under the throttle body.
make sure its working. the tests are in the factory manual.
make sure its electrical connection is clean and good.
when the throttle is not open, the idle setting on that is sending a command to let the ECU know the car is in idle.
The TPS on the L jet is much simpler than the D jet.
its basically an idle setting. and a wide open throttle setting.
all inbetween is run off the AFM to the ECU.

i think mr. perrine is right. its likely to be that harness. its occasionally connecting.
sure sounds like its there.

@wonkipop I'll check the TPS tomorrow. I did check the continuity of terminals 6, 7, 8, 9 from the AFM to ECM and near 0 ohms. The air vane in the AFM actuates the fuel pump relay as well as the fuel pump when the engine is cranked

[JeffBowlsby]

The original L-Jet dual cantilever spring (4 prong) wire terminals wear out or get munched after misalignment during insertion, and updated variations of that style of terminal have dramatically improved over the years.

If the issue is determined to be an electrical connectivity issue look closely at each and every terminal to see if there is a gap between the spring contacts preventing sufficient clamping force to the male counterpart terminal, plating loss, corrosion, grease etc., any of which would inhibit good electrical connectivity.

Most robust available, which I use on my L-Jet harness builds:

[Artfrombama]

I had a leak develop under the fuel tank. Pulled the tank, changed the lines and put it back in. I took it for a drive and it was fine until it died. I stayed near home so I pushed it back and pulled the tank again. When it got warm the fuel line kinked and cut off the fuel. You waited for 3 hours for AAA, I don't think I've ever had vapor lock last that long after the car was off

Bingo!
I pulled the fuel pump (for the fourth time) and noticed no fuel was coming from the supply line. The 9mm line underneath the tank was kinked. Shortened the hoses to remove the loops and all is well. I feel like an idiot for not examining those hoses more carefully.

[wonkipop]

I had a leak develop under the fuel tank. Pulled the tank, changed the lines and put it back in. I took it for a drive and it was fine until it died. I stayed near home so I pushed it back and pulled the tank again. When it got warm the fuel line kinked and cut off the fuel. You waited for 3 hours for AAA, I don't think I've ever had vapor lock last that long after the car was off

Bingo!
I pulled the fuel pump (for the fourth time) and noticed no fuel was coming from the supply line. The 9mm line underneath the tank was kinked. Shortened the hoses to remove the loops and all is well. I feel like an idiot for not examining those hoses more carefully.

f$%k yes.

you are a dead set hero for nailing and posting.
hopefully some other poor bastard stuck in a carpark can go straight to the problem.

go give that humungous 1.8 73 hp hunk of "power" some serious canning. (IMG:style_emoticons/default/beer.gif) (IMG:style_emoticons/default/beerchug.gif) (IMG:style_emoticons/default/biggrin.gif)