L-jet AFM replaced, but the car won't stay running. (SOLVED) Options

[malcolm2]

Update on my post about the BENT AFM. FYI prior to the bending, the car was running great as my daily driver.

I now have a 75 7-pin AFM found on San Diego Craigslist and shipped to TN. I have verified all the proper ohm readings on the connector, fuel pump contacts especially. The flap has full range of motion and the PCB track looks similar to the AFM I removed.

The replacement unit is installed as received and the car will only run (and poorly I may add) if I mash the accel pedal to get about 3000 rpms.

I had planned to go thru the Itinerant ( http://www.itinerant-air-cooled.com/viewtopic.php?t=7761)process today, but I can't get it to idle. I only got as far as setting the MIXTURE screw to the 4-1/2 turn spot.

I do have the new intake elbow on and have tight vacuum line fittings. No vacuum lines appear to be a problem. Triple checking now.

Just tinkering around, I opened the idle screw on the TB, but that did not help.

What do you think? What is next?

Clark

[jim_hoyland]

Open the relay board and look at the 4 spade connector in the lower left corner. Ground the spade in the upper left corner. It's designated III in the diagram.
When you key the ignition, the fuel pump will run without having to rely on the dual relay.
If the engine runs then you have a connection issue at the dual relay

[malcolm2]

No change at all. It will fire up quickly, But takes some accel pedal pumping to get the revs up, then is controlled with the pedal at 2000- 3000.

Remove my foot and drops to a sputter and I turn the key off.

[jim_hoyland]

Disconnect the fuel line and check for flow - carefully....A permanent fuel pressure gauge mounted in line is a great diagnostic tool.

[malcolm2]

I have an in-line fuel press guage. Plenty of pressure.
Here is a shot of the residual pressure after my current shut down. small, fuzzy photo, but it is @ 35 psi.



Not knowing anything about this afm, could the spring tension be tight? The seller said it came out of a 75 914. It seems to have a delayed reaction to the pedal.

I gotta get a helper to crank while i watch.

[timothy_nd28]

Before adjusting the air flow meter, you should double check the basics. Start with making sure that your valve lash is perfect and not too tight, especially the intake valves. This could of been the reason to why the car backfired.

Next, do a compression test on each cylinder. Then post some pictures of the spark plugs. After that, get the car started, manipulate the throttle linkage so that the car stays running. Then remove one fuel injector connector and make sure you hear the engine stumble. Do this for each injector.

It would be nice to verify timing, but this may be hard to do if your car doesn't want to run anything less than 3k rpm.

Next, I would assume your car is inside a warm garage? If so, remove the hoses leading to the aux air valve, temporarily cap at the rubber S boot and cap at the plenum. Do the same for the decel valve. These two items are not critical for the engine to run and would be two less variables to worry about.

Then, read that manual about adjusting the AFM. You really need to borrow your friends air/fuel ratio gauge meter thing to adjust it correctly.

[jim_hoyland]

(IMG:style_emoticons/default/agree.gif)

And : Be sure the resistor pack does not have a broken wire; and check the harness ground is attached tot he spade on the motor

[malcolm2]

Thanks gentlemen. Gives me plenty of things to check. Man do i hate checking the valves. (IMG:style_emoticons/default/barf.gif) I'll add the results as I get them.

I am curious about the PCB differences. They don't look different but the have different part #s on them. The current one has 7805 then 1 288 310 021.

The former one has 9006 then 1 288 310 021. I wondered if they could send different signals. (IMG:style_emoticons/default/dry.gif)

[ClayPerrine]

To quote my father "What was the last thing you F_cked with!"

The description of your problem reeks of false air (air that does not go through the air flow meter on the way into the engine).

Check all the hosts, especially the ones from the AFM to the throttle body. You probably knocked off a line somewhere. No L-Jet car ever built will run with an open hole downstream of the air flow meter. It leans out sooo far that there is just not enough fuel to run.

I would bet on the hose to the aux air regulator or the decel valve.

[malcolm2]

To quote my father "What was the last thing you F_cked with!"

The description of your problem reeks of false air (air that does not go through the air flow meter on the way into the engine).

Check all the hoses, especially the ones from the AFM to the throttle body. You probably knocked off a line somewhere. No L-Jet car ever built will run with an open hole downstream of the air flow meter. It leans out sooo far that there is just not enough fuel to run.

I would bet on the hose to the aux air regulator or the decel valve.

I will go thru all the vac hoses once again this evening. (procrastinate before I get to Tim's list) (IMG:style_emoticons/default/hissyfit.gif)

In post 5 above I added a photo of my fuel press gauge. You can see the DECEL vac line folded, plugged and wire tied. I have not had a DECEL valve in operation in 3 years... since the beginning. (IMG:style_emoticons/default/shades.gif)

I hope you are correct about a vac leak, Tim has been saying the same thing. If there is one, it is not very obvious. I guess I should just remove everything and re-seat the hoses.

A few months back, I seem to remember accidently not replacing the DECEL hose from the air distributor for some reason.... and the car did act very similar to the way it is acting now.

Thanks to all for your input.

[ClayPerrine]

To quote my father "What was the last thing you F_cked with!"

The description of your problem reeks of false air (air that does not go through the air flow meter on the way into the engine).

Check all the hoses, especially the ones from the AFM to the throttle body. You probably knocked off a line somewhere. No L-Jet car ever built will run with an open hole downstream of the air flow meter. It leans out sooo far that there is just not enough fuel to run.

I would bet on the hose to the aux air regulator or the decel valve.

I will go thru all the vac hoses once again this evening. (procrastinate before I get to Tim's list) (IMG:style_emoticons/default/hissyfit.gif)

In post 5 above I added a photo of my fuel press gauge. You can see the DECEL vac line folded, plugged and wire tied. I have not had a DECEL valve in operation in 3 years... since the beginning. (IMG:style_emoticons/default/shades.gif)

I hope you are correct about a vac leak, Tim has been saying the same thing. If there is one, it is not very obvious. I guess I should just remove everything and re-seat the hoses.

A few months back, I seem to remember accidently not replacing the DECEL hose from the air distributor for some reason.... and the car did act very similar to the way it is acting now.

Thanks to all for your input.

Check to make sure the hose from the AFM to the throttle body is still connected on the throttle body end. If it gets disconnected accidentally, it usually opens up a gap on the bottom where you can't see it.

I paid for a factory L-Jet class about 28 years ago. That is probably the most useful factory training I ever got.

[Mark Henry]

I have an in-line fuel press guage. Plenty of pressure.
Here is a shot of the residual pressure after my current shut down. small, fuzzy photo, but it is @ 35 psi.



Not knowing anything about this afm, could the spring tension be tight? The seller said it came out of a 75 914. It seems to have a delayed reaction to the pedal.

I gotta get a helper to crank while i watch.

Unless you can see that gauge when sitting in the drivers seat it isn't worth a pinch of dog poo.
Did you have the tank out, a pinched/kinked line at the tank will drive you bat shit.

[malcolm2]

I have an in-line fuel press guage. Plenty of pressure.
Here is a shot of the residual pressure after my current shut down. small, fuzzy photo, but it is @ 35 psi.



Not knowing anything about this afm, could the spring tension be tight? The seller said it came out of a 75 914. It seems to have a delayed reaction to the pedal.

I gotta get a helper to crank while i watch.

Unless you can see that gauge when sitting in the drivers seat it isn't worth a pinch of dog poo.
Did you have the tank out, a pinched/kinked line at the tank will drive you bat shit.

Oh I disagree on the gauge.... Anytime I have issues, someone always asks about the fuel pressure. And it would take time to install one, every time someone asks, or I want to know. Really it is for troubleshooting.

The tank has not been out since 2012. But being a 75 the pump is in the front and a couple months ago I pulled the pump and the filter out from under the tank to verify operation and kink-less hoses. For now it is just lying in the trunk, lazy-ness on my part. So I believe the hoses are still not kinked.

BTW: I had to work on the Volvo last night and tonight I am going to the Ryman to see Robert Earl Keen (IMG:style_emoticons/default/shades.gif) So the 914 has taken a back seat 'til Thurs or Fri. More to come soon tho. Not switching to carbs just yet.

[McMark]

The AFM could be bad or maladjusted as well. Fuel Injection Corp rebuilds them. I've used a bunch of them. It's great peace-of-mind to know it's fresh and calibrated correctly.

[malcolm2]

The AFM could be bad or maladjusted as well. Fuel Injection Corp rebuilds them. I've used a bunch of them. It's great peace-of-mind to know it's fresh and calibrated correctly.

So when you install them.... the car starts right up?

I wondered about the condition of this one, being used and previously rebuilt by out-of-business PYTHON.

Is there any way to further test the operation? Physically the flap opens smoothly, the track has marks, but is not worn thru, neither was my BENT one. I have done the ohms tests on all the connections, verified and cleaned up the FP contacts and the swivel contact on top of the swiper, what else is there to verify?

I would think I would get varying readings as the arm moves (flap opens), right. I have not done that yet, but don't know the spec per degree of motion.

I saw a test on the samba about a 60 gram weight on the flapper, have not read completely thru that yet. At this point, I am praying for a vacuum leak. (IMG:style_emoticons/default/driving-girl.gif)

I hate it when my paying job gets in the way of fixing this car!!!

[jim_hoyland]

Perhaps you could borrow a known "good" AFM and swap it in- that will tell you more?

[McMark]

Yup, plugged in and fired up.

I don't know of any reliable tests, but I take a much more quantitative approach then most. If I were setting up to test an AFM, I would want to graph airflow vs. signal output across a range. Then compare to a known good baseline. But in shop time that's $1,000,000. (IMG:style_emoticons/default/icon8.gif) So just replacing it with a rebuilt and calibrated unit, to me, is a 'shortcut'.

You may have a vacuum leak, and the AFM may be fine - So I'm not suggesting a new AFM will cure your issue. But just sharing my perspective that I hate dealing with unknowns and I find it worthwhile to simply pay a little extra and at least know what I'm starting with.

[malcolm2]

Perhaps you could borrow a known "good" AFM and swap it in- that will tell you more?

I have been offered one to test.... I hate the thought of BENDING someone else's $300 part.

I will go thru all the suggestions here by the weekend, I hope. They should remove all other doubt. Then check and see if the offer to loan is still good. And then I may have to breakout the checkbook on a freshly re-built, known good one.

Thanks again.

[ClayPerrine]

I have a factory calibration tool for the AFM in my toolbox.

It is not easy to use, and it requires patience. But it can be done.

I also have about 30 old AFMs. Some are bent, some are completely scrap and some work. The factory L-jet tester I have only partially works because it got immersed in water at some time in the past.

Simpler to use a volt meter.

[malcolm2]

BACK TO 914 TROUBLESHOOTING: I finally carved out some time to dig into this problem. Before I got to Tim's list of goodies, I decided to dive into vacuum leak detection.

I felt like my hoses and intake boot were tight. Everything was new. I checked a few other hoses.

DECEL: As stated earlier, the decel has been removed. I capped and folded the large hose securely. However, it easily slipped off of the connector on the Air Distribution box.

I have never been positive that #3 intake was perfect. The pipes just don't line up. #3 is on the left below. They are also too far apart to use the pretty cloth hose. I bought a radiator hose and cut it. Might have still been too short. Notice the curve. When mounted one edge was lifted up.





3/4 side INTAKE: Again as I removed these hoses, they slide off fairly easily. During this tedious removal, I noticed that the phenolic block was cracked in between the ports. Another find.... The nuts holding the intake to the head required very little effort to break the torque. Not loose but just better than "hand tight". The paper on the phenolic was brittle, cracked and delaminating from the block.



During removal, I realized that maybe I did some OVER INSTALLING of the seal kit. Probably a bad time to ask, but does anyone use the metal seals with the phenolic block on FI installs? (IMG:style_emoticons/default/headbang.gif)

About 30,000 miles on all this. I plan on purchasing new hoses and intake seals today. I also plan on NOT using metal seals under and over the phenolic block.

Please chime in, could the cracked block and easily removable (not snug) hoses be the trouble?