75 still running rich, 75 still running rich Options

[N_Jay]

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

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)


(IMG:style_emoticons/default/wink.gif)

[brooks944]

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

[brooks944]

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

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

[malcolm2]

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

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.... (IMG:style_emoticons/default/piratenanner.gif) (IMG:style_emoticons/default/piratenanner.gif)



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

Do you have a way to test the fuel pressure?

[malcolm2]

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. (IMG:style_emoticons/default/shades.gif)

[malcolm2]

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

[914_teener]

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

[malcolm2]

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.

[brooks944]

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

[brooks944]

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).

[malcolm2]

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

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

[brooks944]

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

[brooks944]

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.

[malcolm2]

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?

[Bartlett 914]

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.