My 75 is running rich and fouling plugs after just a few miles. One of the members spent several hours helping me check and figure out the FI a couple of years ago and that made a difference (both on the car and how much I value your experts here). I have 2 extra 'brains' is it time to change that and check? One is from a '75 and one from a 74, does that matter? Both are for a 1.8 which my car is. Fuel injectors are rebuilt as well as the cold start valve. Most vacuum hoses changed. Thanks for any input.

Rick

Check the pin count on the ECU. Some have six and some have seven. I believe a '75 1.8 L-Jet ECU has seven.

Not sure what that you mean, thanks for replying!

Probably a dumb reply, but do you have pics of what I should be looking for?

He may be referring to the connector at the AFM; some are 6 pin, others 7. The AFM has to be compatible with the ECU. Don' have the part numbers handy, but they have been posted several times

Sorry My Bad. I meant AFM not ECU

Check this out for a good read. Not exactly 914 subject matter but close enough.

http://www.firstfives.org/faq/ljet/jetronic.pdf

Thanks, is the probable issue the AFM instead of the brain?

So, did this just happen? Did something change, or has it been doing this for a long time?

You said the Injectors were rebuilt. When? Did you put them right in? They can gum up with the rebuilding fluid if you let them sit a while. I had to send mine back so they could clean them just before I was ready to crank.

The injectors were rebuilt a couple of years ago and installed into the car when they came back.

Also, the 75 has seven pins (I also have a 74 and the connection to the man on that car has 6).

So you can't use a 74 6-pin AFM on the 75 7-pin harness.

If either AFM ever becomes totally unobtainable, I am sure with some studying of where the pins go etc...they could be made to work properly. Until then, if you want one for your car, buy a 7-pin one.

If the flap moves freely and no one has messed with the spring or gear then it is probably not bad. Sometimes you can tell just by trying to remove the plastic lid. If it is tuff to get off and the seal looks good, it my be a virgin.

They can be tested. Can't remember if I did, but I do remember checking into bench testing.

The bent flap is a dead give-away. But that causes a no-run, no-idle, no-start problem, not a rich issue.

You still might want to test them, Cold Start valve too. Checking the squirt pattern, volume and to see if they leak. Poor pattern or leaking would sure cause a rich issue.

I'll see if I can find a post when Tim helped me do that. IIRC we jumped some wires turned the key and I operated the AFM flap while the injectors sprayed into jars. Again, IIRC you do 1 side at a time. You can compare the output, pattern and leaking with one 5 second squirt.

BTW is your 75 a true 1.8 (1756cc) or has it been upgraded to a 1911?

Clark

cht sensor is bad I would say if the afm is not stuck

Tim did help me check out the maf, it worked fine. My car has been modified to 1911cc. It sounds to me more and more like the chat sensor. These don't seem to be that expensive, are they hard to replace?

Thanks everyone for the help!

Here is a simple test for you to try....

study up on Jeff's ECU wiring layout. HERE... http://bowlsby.net/914/WiringHarnesses/Har...FI_EC75-1.8.pdf

Disconnect your ECU connector. Set your Volt meter on OHMS and put one lead on the pin of the connector labeled 13 in the link above. That wire goes to the CHT.

Put the other one on metal somewhere on the car (bare metal, not paint), or the negative post on the battery.

Tell us the result on the meter.

Here are some pictures of the spark plugs, probably less than 50 miles. Thanks everyone for your help.Click to view attachment

As some have stated, could be CHT, my money is on a vaccuum leak. Buy a tester and start checking each part.

Thanks, what do I need for a vacuum leak. Changed too many hoses and did the cigar test!

I made me a smoke tester. Couple pieces of charcoal in a fresh paint can from HD. Compressed air in, smoke out. attach to a vac line on the car and see where the smoke comes out. I will find my post and link it here.

http://www.914world.com/bbs2/index.php?s=&...t&p=2450938

Did you check your CHT: ECU 13 to ground yet?

Hi Rick, I've been following this thread but too busy to put much thought into your issues. I'm preparing for the MCAT exam this week which has been nonstop studying.
Clark (Malcom2) will help walk you through, especially if you have any vacuum leaks.
Heed his advice and don't replace any parts until you have thoroughly tested them.

It is cursed! For a small fee I will remove it from your home, and have it exercised so it does not haunt you any more.

(P.S. If rust free, the fee can be waived)

Clark, I got 1.376k ohms when pin 13 was connected to neg battery post.

Tim, good luck on your test and thanks for your help!

N jay, the car is for sale, bring $.

Tim tells me that the CHT probably would not fail on one end of the graph and not on the other. But since we have a graph, I might do the 13th pin test after a long idle to heat up the cylinder head (key off of course), just for proof....

Click to view attachment

So did you change the ECU.... if you did, which year did you install?

Do you have a way to test the fuel pressure?

Click to view attachment


if you can find a way to check your fuel pressure, you can then bypass the CSV and check fuel pressure at high RPM and at idle. One way is like the purple line above. Or get a hose union and pull the hoses from the CSV and connect them together.

make the by-pass semi-permanent (decent clamps if needed) so you can drive a while and maybe recheck your plugs.

It seems that every time I have trouble, someone always asks about fuel pressure. So I bought a Harbor Freight fuel injector test kit, I guess it is. I installed the gauge between the passenger side metal fuel rail and the CSV. (green circle above)

No, I can't see it when I am driving, but I can see it when I open the hood.

Just had a thought.... when you pull the hoses on the CSV you can use the TEE from the harbor freight FI kit and mount the gauge there. Kill 2 birds. 1. take the CSV out of the loop, 2. put a pressure gauge in the loop.

https://www.harborfreight.com/fuel-injectio...ster-62623.html

I just use the screw tee hole on the driver side fuel rail and use the adapters in the HF kit.

There you go.

I never messed with the metal rail fitting. It is so small.

OK, got the HF fuel injector kit and measured pin 13 to battery negative after warming the car up. The fuel pressure was about 32 psi, but bouncing from 30 to 40. At higher rpm (3k plus), steadied at 32 psi. After the car warmed up I measured pin 13 to negative battery post and it read 67 ohms and was increasing as the car cooled. is it the CHT sensor? Appreciate everyone's help.

Rick

Also, I did change the ECU yet. I have what seems to be a 75 and a 74 (based on the color of the stickers).

Man, you are on it. I meant to post a pic of my fuel pressure set up. You might want to find a way to have the gauge on there all the time.

Sensor seems good. Check out the chart. at 67 ohms your cylinder head must have been over 300*f. you got 1300-ish ohms at 75*F. That is what you should expect.

Pressure seems right too. Mine jumps around too. I am in the same range 30-40.

You said it felt smoother, have you driven any? still smooth? Maybe you can pull a plug and check the electrode, post a picture.

Hey, what about that ECU question? You did or did not swap one out? Are you sure the 75 spare ECU is mounted and not the 74?


BTW, here is my FP gauge DIY permanent installation.

http://www.914world.com/bbs2/index.php?s=&...t&p=2437471

Thanks. Did not change the ECU yet. It did run smoother again today, still assume it's the fresh plugs. But still smells rich.

Here is a couple of pictures of the plug from cylinder 3. New plug only in the car long enough to do the testing suggested. Looks pretty black... appreciate any suggestions.

So who has more ideas about running rich? All 4 cylinders, right Rick?

Rick and I have been trying things.

* CHT ohms test was correct at room temp and 300*
* spare '75 ECU found no benefit.
* fuel pressure is normal
* Cold Start Valve is unplugged and replaced with a fuel pressure gauge.
* fresh plugs were fouled very quickly as pictured

At this point he is going by smell, but he is trying to borrow an A/F rig to pin-point how much rich.

I sent him the Itinerant posting about "asking the car what it wants", he may learn from that.

Mentioned that he might want to check (one cause they all should be checked, but also to eliminate some mechanical probs.)
*compression
*valve clearances
*and timing

But what makes the whole system rich?

I would guess the AFM is messed up. Maybe the relationship between the flapper and the pot internally is out of position with each other telling the ECU the flapper is open more than it actually is.