Injection experts...please advise...?
11-13-2007, 07:46 PM
#31
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No biggie, sir...but be gentle with me...it's fairly easy to confuse me...
The fact that at very low fuel pressure your CO drops after connecting the sensor shows that the O2 loop is doing what is should. The problem is that its range of control is about +/- 20% on injector time.
If you do have 30# injectors, then they flow about 25% more than the stock 24# so you shouldn't have to back off the fuel pressure by much to get the O2 loop within range. Especially if you have also turned the CO pot on the MAF down to minimum.
Injector flow rate will drop by square root of pressure change, so if you are turning 40psi injectors down to 4psi flow rate will drop by factor of 3 or so.
Something doesn't stack up..... like Tampa said
If you do have 30# injectors, then they flow about 25% more than the stock 24# so you shouldn't have to back off the fuel pressure by much to get the O2 loop within range. Especially if you have also turned the CO pot on the MAF down to minimum.
Injector flow rate will drop by square root of pressure change, so if you are turning 40psi injectors down to 4psi flow rate will drop by factor of 3 or so.
Something doesn't stack up..... like Tampa said
Which is why I've been thinking the brain might be schmeefed. Is there a failure mode in which the brain otherwise continues to function, but delivers a maximal pulse? (But, jumping the WOT jumpers did make it worse). And this failure mode would also have to be consistent with the fact that the lambda loop obviously does something, when the fuel pressure is down to practically nothing, the CO is in an earthly range, and the O2 sensor is re-connected.
If not, I suppose I'll try to pull one and see if I can glean what it is. Will I be able to identify it by getting a name and numbers off of it? I don't remember my stock injectors (on my euro) saying much of anything, but I could be wrong.
12-13-2007, 03:01 PM
#33
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AHA... (?!)
Was unplugging the MAF for last time today, after having moved it back up to engine compartment to see if the thing would work right if I eleminated the extension harness, even though it ohmed-out OK. No go...so was going to ship the MAF and the LH brain to Mark, who also has an 86 using this brain, to see if my combo screwed his car up, as well...
...and I saw a FRAYED wire, previously undetected, on the MAF plug. Dunno which term it goes to, didn't disassemble the whole thing. Decided to repeat all tests between LH brain plug and the MAF connector: all OK, 1,3,5,6 zero ohms to LH brain connector, or very near.
Also decided to repeat the test btwn term 2&4 of MAF, 4 being ground if memory serves, and 2 being battery voltage...the voltage measured was 3 volts - this gotten by removing relay XVI and jumping trms 30 & 87, per WSM procedure. Mind you, the last (first) time I did this test, the voltage was a little low (I'm thinking it was about 11.5 volts), but I thought it might be due to the fact that I also had the ignition on, and there's a huge cooling fan that starts running when you turn on the igntion, could drop the battery voltage a bit, also my meter is not necessarily a Fluke.)
I'll bet *this* could cause my problem...Thoughts, John? I'll disassemble the AMP plug and try to repair it, or just go to RadShack and create something. If I find that it's not the frayed connection that's guilty, I wonder how you all would approach finding the deficit. From where cometh the voltage to the dreaded MAF term 2?? (yes, relay XVI, I know, but it's out and jumped).
Thanks in advance
Clay
...and I saw a FRAYED wire, previously undetected, on the MAF plug. Dunno which term it goes to, didn't disassemble the whole thing. Decided to repeat all tests between LH brain plug and the MAF connector: all OK, 1,3,5,6 zero ohms to LH brain connector, or very near.
Also decided to repeat the test btwn term 2&4 of MAF, 4 being ground if memory serves, and 2 being battery voltage...the voltage measured was 3 volts - this gotten by removing relay XVI and jumping trms 30 & 87, per WSM procedure. Mind you, the last (first) time I did this test, the voltage was a little low (I'm thinking it was about 11.5 volts), but I thought it might be due to the fact that I also had the ignition on, and there's a huge cooling fan that starts running when you turn on the igntion, could drop the battery voltage a bit, also my meter is not necessarily a Fluke.)
I'll bet *this* could cause my problem...Thoughts, John? I'll disassemble the AMP plug and try to repair it, or just go to RadShack and create something. If I find that it's not the frayed connection that's guilty, I wonder how you all would approach finding the deficit. From where cometh the voltage to the dreaded MAF term 2?? (yes, relay XVI, I know, but it's out and jumped).
Thanks in advance
Clay
Last edited by gasmanstl; 12-13-2007 at 09:41 PM. Reason: typo
12-13-2007, 04:40 PM
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12-16-2007, 09:18 PM
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Next episode:
It's better, but it's still not really right.
I totally rewired the MAF connector and got another harness plug to allow me to either plug into the extension harness for under-car MAFing through turbo, or to plug the original AMP connector into it, to either test the MAF in the engine compartment, which I did today, or if myself or someone else wants to take off the turbo.
Voltage is now battery voltage between trms 2 and 4. But I was an idiot: when I found the frayed MAF wire and repeated all those tests, I forgot to plug the brain back in when I tested the V btwn trms 2 and 4!! I had been all busy ohming out 1,3,5,6 through the LH plug. Still, it was funny...I got 3 volts when I jumped relay XVI with brain d/c...then when I fixed the MAF wires, it was 1.5 volts...go figure. Something definitely changed. Then I figured out that I had left the brain d/c'ed.
OK, so I put it all back together and ran/tested it again today. Now, I am able to get the CO in the 1% range with the fuel pressure set at 15 PSI, and the adjustment pot on the MAF turned all the way out so that the resistance between pin 6 and the body of the MAF is zero ohms...the leanest setting. But it doesn't stay there...it will suddenly rise to 5-6%, then drop back down again.
I really think the computer is bad.
So I'm sending Mark the MAF and the LH brain. He has offered to apply these to his identically-equipped car and see what they do to it.
I'll keep you posted.
I totally rewired the MAF connector and got another harness plug to allow me to either plug into the extension harness for under-car MAFing through turbo, or to plug the original AMP connector into it, to either test the MAF in the engine compartment, which I did today, or if myself or someone else wants to take off the turbo.
Voltage is now battery voltage between trms 2 and 4. But I was an idiot: when I found the frayed MAF wire and repeated all those tests, I forgot to plug the brain back in when I tested the V btwn trms 2 and 4!! I had been all busy ohming out 1,3,5,6 through the LH plug. Still, it was funny...I got 3 volts when I jumped relay XVI with brain d/c...then when I fixed the MAF wires, it was 1.5 volts...go figure. Something definitely changed. Then I figured out that I had left the brain d/c'ed.
OK, so I put it all back together and ran/tested it again today. Now, I am able to get the CO in the 1% range with the fuel pressure set at 15 PSI, and the adjustment pot on the MAF turned all the way out so that the resistance between pin 6 and the body of the MAF is zero ohms...the leanest setting. But it doesn't stay there...it will suddenly rise to 5-6%, then drop back down again.
I really think the computer is bad.
So I'm sending Mark the MAF and the LH brain. He has offered to apply these to his identically-equipped car and see what they do to it.
I'll keep you posted.
12-16-2007, 09:46 PM
#38
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I'm not sure if it has been mentioned, but have you run a fuel pressure drop test. Possibly a small leak causing rich condition. If you can force a lean condition and 02 responds like you said it might be in a different area. Loaded up spark plugs or contaminated oil could also cause this. Just a thought.
12-16-2007, 11:23 PM
#39
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I'm not sure if it has been mentioned, but have you run a fuel pressure drop test. Possibly a small leak causing rich condition. If you can force a lean condition and 02 responds like you said it might be in a different area. Loaded up spark plugs or contaminated oil could also cause this. Just a thought.
I'm not sure I know what a fuel pressure drop test is. Are you referring to a stuck or leaking injector? I have thought of this, but I have not considered it seriously because of the fact that when you turn the car off, the line pressure *holds*. For hours and days. I have a gauge on one rail. So if I had a leak, it would leak down...right?
If you're talking about something else, then I'd like to hear more. Thank you for your help.
12-16-2007, 11:45 PM
#40
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Most vehicles will bleed down overnight, there is a test procedure in the WSM. If yours holds pressure that long, then injectors, dampers and regulator should be fine. Fuel contaminated oil can be mis-leading at times when diagnosing.
04-09-2008, 05:05 PM
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MAF has been proven to be bad.
Sent my LH and my MAF to Mark Robinson, the original owner of the car and also the owner of an identically-equipped, rear-turbo'ed 86 S, a 'duplicar.'
The brain worked fine, his car ran fine on it.
The MAF choked the car to pieces, ran in the low 12's A/F ratio per his wideband meter, and fouled his plugs in minutes.
Although he, and others have tried to tell me it was the MAF, I simply wouldn't believe it, since it was a fresh refurb, and passed the WSM tests...
Gawd. I've been at this a year.
The brain worked fine, his car ran fine on it.
The MAF choked the car to pieces, ran in the low 12's A/F ratio per his wideband meter, and fouled his plugs in minutes.
Although he, and others have tried to tell me it was the MAF, I simply wouldn't believe it, since it was a fresh refurb, and passed the WSM tests...
Gawd. I've been at this a year.
04-09-2008, 06:25 PM
#43
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Sent my LH and my MAF to Mark Robinson, the original owner of the car and also the owner of an identically-equipped, rear-turbo'ed 86 S, a 'duplicar.'
The brain worked fine, his car ran fine on it.
The MAF choked the car to pieces, ran in the low 12's A/F ratio per his wideband meter, and fouled his plugs in minutes.
Although he, and others have tried to tell me it was the MAF, I simply wouldn't believe it, since it was a fresh refurb, and passed the WSM tests...
Gawd. I've been at this a year.
The brain worked fine, his car ran fine on it.
The MAF choked the car to pieces, ran in the low 12's A/F ratio per his wideband meter, and fouled his plugs in minutes.
Although he, and others have tried to tell me it was the MAF, I simply wouldn't believe it, since it was a fresh refurb, and passed the WSM tests...
Gawd. I've been at this a year.
If the kit was setup with an aged MAF, then it may not be OK with a rebuilt MAF in calibration. The other possibility is that you may have damaged the MAF with your problems with the wiring harness.....
04-14-2008, 10:42 PM
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The problem is solved...hooray...
And that it did. When I heard from Mark that it was definitely whacked, I just went to the phone and ordered a used one. Went out to the garage and cranked the fuel pressure back up to the reasonable range (mid 20's)...plugged my brain back in...and she was actually running a bit lean. So I cranked the fuel pressure back up to 35, and that richened her up into the 13's by my Heathkit Exhaust Gas Meter. Piddled around with the mixture pot on the MAF, and rechecked the meter for drift a few times, and she was running 1% CO "before the cats" (which is everywhere on this car, right now
) in no time. All of this done with the WOT/idle plug unplugged and a jumper between Trms 1 and 2, to remove any ambiguity concerning my idle switch, which needs replacement.It was interesting to watch the effect of this switch on the mixture. Adjust mixture as above, remove the jumper (thereby simulating "driving-down-the-road-and-tooling-around" mode), and the mixture richens just a little bit, maybe to 2% or so, I wasn't memorizing the A/F numbers. Jump Trms 2 and 3, thereby simulating WOT, and it just richens the bejezus out of it, to like 6-8%. I don't know if this is normal behavior or not...it could be that my O2 sensor, even though "new" but exposed to the toxic waste produced by the old MAF, is once again in need of replacement.
At any rate, I am a very happy man to finally have the solution to this problem. John, I believe that Mark is shipping the MAF in question to you. I'll be fascinated to hear the post-mortem. I'm sure it just got smacked a little hard on the trip across the pond, in an excedingly bad (and confusing) piece of luck for myself.
