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New fuel delivery (?) issue?
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bureau13  



Joined: 07 Sep 2017
Posts: 310
Location: South Florida

PostPosted: Thu Aug 27, 2020 2:38 pm    Post subject: Reply with quote

You are definitely correct about #1!

The problem is that it idles great, but at very light throttle, ie driving away slowly, it starts to buck and surge and that corresponds to the lean spikes. It very much is not just a wideband issue.

I then did a smoke test, found and fixed vacuum leaks, same problem. Did another smoke test, found and fixed more vacuum leaks, same problem. Smoke test now seems good. Tested frequency valve operation best I could, I can't really measure duty cycle but it *seems* to be behaving as expected.

I have a recently-installed Mittelmotor distributor running my ignition, which was working great initially. Could something be happening with the ignition? I guess it's possible? I'm not getting into boost or high RPMs at all when the problems happen though. The lean spikes made me think fuel, but I guess you're right that misfires might show up as lean.

Vacuum leak really did seem like the perfect answer. And I had them! And yet still after fixing several of them, nothing has changed.

kondzi wrote:
Didn't have time to read the whole thread... So sorry if I misinterpret something

1. Fixing one thing in these classic old cars usually means there will be something else to fix soon. You might have done good job with TB rebuild, but something else, not considered before is messing this up.
2. Vacuum leak is usually observed with idle and low RPM range. When you open TB, the percentage of air via vacuum leak is minority and doesn't change much.
3. Can you record these leans spikes on the gauge by your phone or sth and share it? I've seen faulty WB controllers behaving strangely. Do you feel these spikes on the way how the car rides, or it's just the reading?
4. You can try to blow compressed air into intake (via sealed and opened TB) and listen with your ear where it's coming out of the pipes. Just an idea, but helped me once.
5. Lean AFR spike can be caused by misfire. Oxygen is not burn resulting in lean reading at the WB controller. Maybe thatís the reason?

_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 2008
Location: Somerset, UK

PostPosted: Thu Aug 27, 2020 5:20 pm    Post subject: Reply with quote

FPR cutting the fuel pump
Overboost switch not earthed or failed, cutting the fuel pump
(Wrong map in the dizzy?)
_________________
1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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bureau13  



Joined: 07 Sep 2017
Posts: 310
Location: South Florida

PostPosted: Fri Aug 28, 2020 12:25 pm    Post subject: Reply with quote

I bypassed the overboost switch, no change. I don't think it's the map, it's the same one I've been running with all along...the FPR cutting the fuel pump issue...now that is a new one to me? How does that happen/how do I test for that? FPR is in the fuel distributor on these cars? Or am I way off?

Carrera RSR wrote:
FPR cutting the fuel pump
Overboost switch not earthed or failed, cutting the fuel pump
(Wrong map in the dizzy?)

_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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bureau13  



Joined: 07 Sep 2017
Posts: 310
Location: South Florida

PostPosted: Wed Sep 02, 2020 9:05 am    Post subject: Reply with quote

I honestly don't know what else to test, but I think a basic CIS test is in order. Now, supposedly my fuel distributor was "rebuilt" before I bought it, but at the very least if I test line and control pressure and it's where it should be (or if it isn't!) then I'll know. I never bothered to get a CIS test set because there was no indication that it wasn't working properly (and in fact I think it WAS working properly) but it's something I should have and know how to do anyway.
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 2038
Location: MI

PostPosted: Wed Sep 02, 2020 11:11 am    Post subject: Reply with quote

Can you make a video of the symptoms in action?
Is it really like lean spikes where it cuts in and out or more like a lean spot in the tune?
Does it do it if you just hold like 4K rpm with no load?
Have you tried driving with the fuel pump jumped or just put a regular 30/87 relay in it?
Does your tach drop out at all?
Check your fuel pump contacts at the fuse, contacts on pumps, ground at the rear ground crown by the left rear tail light?
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bureau13  



Joined: 07 Sep 2017
Posts: 310
Location: South Florida

PostPosted: Wed Sep 02, 2020 1:24 pm    Post subject: Reply with quote

I need to try to do that (the video). It's definitely most obvious if you try to actually drive it, but I can make it happen in neutral. "Spikes" may be a poor choice of words. Driving, I can see the AFR jump up to 15 and above, it doesn't stay there but of course I'm not holding the gas there either. I neutral you can hear a difference and see the AFR go up as well. Last time, I tried it very gradually but I don't remember what RPM it started happening, or if it was repeatable in exactly the same way. I'll get a video of all that.

I have done this with the a jumper in place of the relay, no change. I have not seen the tach drop out, and I will check those contacts and grounds.

Thanks

Fasteddie313 wrote:
Can you make a video of the symptoms in action?
Is it really like lean spikes where it cuts in and out or more like a lean spot in the tune?
Does it do it if you just hold like 4K rpm with no load?
Have you tried driving with the fuel pump jumped or just put a regular 30/87 relay in it?
Does your tach drop out at all?
Check your fuel pump contacts at the fuse, contacts on pumps, ground at the rear ground crown by the left rear tail light?

_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 2008
Location: Somerset, UK

PostPosted: Wed Sep 02, 2020 6:53 pm    Post subject: Reply with quote

bureau13 wrote:
I bypassed the overboost switch, no change. I don't think it's the map, it's the same one I've been running with all along...the FPR cutting the fuel pump issue...now that is a new one to me? How does that happen/how do I test for that? FPR is in the fuel distributor on these cars? Or am I way off?

Carrera RSR wrote:
FPR cutting the fuel pump
Overboost switch not earthed or failed, cutting the fuel pump
(Wrong map in the dizzy?)


You are way off. Its a relay on the fuse panel. If the FPR has cut power to the fuel pump then it can idle but will not supply enough fuel to drive.....causing lean 'spikes'

How did you bypass the overboost?
Have you jumped the relay to rule out the FPR?
Have you tested the volts supplied to the fuel pump? A voltage drop will make the pump run slow or not at all. Have you checked and cleaned the pumps connections?

Then 100% do a system pressure check, check the WUR for debris, check the injectors for fuel flow and spray pattern.

As for the map, I think I mentioned my thoughts on that via Facebook......it doesn't sit with me right. Check the fuel out as above and get it on a dyno with someone who can set up the map and fuelling. Dyno's are for testing and fault finding not just for proving your bhp.
_________________
1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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bureau13  



Joined: 07 Sep 2017
Posts: 310
Location: South Florida

PostPosted: Thu Sep 03, 2020 8:00 am    Post subject: Reply with quote

Lol I thought that didn't make a lot of sense! I've never seen FPR used to mean the fuel pump relay, but yes, I have bypassed that with a jumper, it made no difference.

I tested the overboost switch by removing the wire and grounding it. No change.

I will check out the connections to the fuel pump, etc.

Regarding the map, I tweaked the areas you were concerned about, but I don't see how they could be in play here. Those were higher in the rev range, I am not near those RPMs when I have problems. Also, while you are 100% right about the dyno tuning, etc, I was driving with this map with no problems that I could tell. Now, that doesn't mean it wasn't risky running that much advance, but if that map at least seemed fine at first, I don't see how it could cause the problems I'm having now. There is no way for this car to "seem fine" the way it's behaving at the moment!

Carrera RSR wrote:
bureau13 wrote:
I bypassed the overboost switch, no change. I don't think it's the map, it's the same one I've been running with all along...the FPR cutting the fuel pump issue...now that is a new one to me? How does that happen/how do I test for that? FPR is in the fuel distributor on these cars? Or am I way off?

Carrera RSR wrote:
FPR cutting the fuel pump
Overboost switch not earthed or failed, cutting the fuel pump
(Wrong map in the dizzy?)


You are way off. Its a relay on the fuse panel. If the FPR has cut power to the fuel pump then it can idle but will not supply enough fuel to drive.....causing lean 'spikes'

How did you bypass the overboost?
Have you jumped the relay to rule out the FPR?
Have you tested the volts supplied to the fuel pump? A voltage drop will make the pump run slow or not at all. Have you checked and cleaned the pumps connections?

Then 100% do a system pressure check, check the WUR for debris, check the injectors for fuel flow and spray pattern.

As for the map, I think I mentioned my thoughts on that via Facebook......it doesn't sit with me right. Check the fuel out as above and get it on a dyno with someone who can set up the map and fuelling. Dyno's are for testing and fault finding not just for proving your bhp.

_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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bureau13  



Joined: 07 Sep 2017
Posts: 310
Location: South Florida

PostPosted: Thu Sep 03, 2020 9:02 am    Post subject: Reply with quote

This folder contains a video of me slowly bringing the RPMs up in neutral. AFRs are on the right, you can see them start to jump around as the revs get higher. I stop around 3K or so, maybe a little less. There is also a screenshot of the 123Ignition dashboard, so you can see vacuum and ignition advance near the top of that "run."

It might not be so obvious, but the car starts to break up as the AFRs start to jump around. It's way more obvious when trying to drive, but also harder to film

https://photos.app.goo.gl/S8KvudaSFF2U6sWq7
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 2038
Location: MI

PostPosted: Thu Sep 03, 2020 12:01 pm    Post subject: Reply with quote

Ignition...

Mine runs fine up into the mid 16s, 15s donít make it run poorly..
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bureau13  



Joined: 07 Sep 2017
Posts: 310
Location: South Florida

PostPosted: Thu Sep 03, 2020 1:41 pm    Post subject: Reply with quote

Hmmm...would the ignition cause it to be up in the 15s and 16s though? It never used to. Also, something to keep in mind, the problem does seem more severe under some load. I've seen 18s, not steadily but I've seen it.

Given I have this Mittelmotor distributor thing, which removes the DITC and ignition amplifier thingy up behind the headlight, I'm not sure how to dig into it. Plugs and wires are all new. I honestly was wondering if the distributor stopped "doing its job properly," but if you look at my dashboard snapshot, the advance is right about where it should be according to the map, and that map ran fine, right up until it didn't.

Actually the coil is not new. I hate just fixing random things, but it's the one not-new piece of the ignition...does that seem like a plausible item that could cause this?

Fasteddie313 wrote:
Ignition...

Mine runs fine up into the mid 16s, 15s donít make it run poorly..

_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 2038
Location: MI

PostPosted: Fri Sep 04, 2020 1:59 am    Post subject: Reply with quote

Yeah maybe..
Maybe it doesnít have enough dwell which causes a problem as rpm increases?
I donít know how that distributor works..

Ignition misses would show lean on the AFR gauge.. Does the exhaust smell like unburnt gasoline when it happens? (Which would also mean unburnt oxygen ie read lean)

Any chance your distributor thing is wrong about where it thinks tdc is?
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 2038
Location: MI

PostPosted: Fri Sep 04, 2020 2:36 am    Post subject: Reply with quote

I just tested and it will run all the way up to 18 AFR and not cut out like your car does...

https://youtu.be/wwGYwV9Rqoc

So Iím pretty sure yours is an ignition problem..
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 2008
Location: Somerset, UK

PostPosted: Fri Sep 04, 2020 5:04 am    Post subject: Reply with quote

Fasteddie313 wrote:
Any chance your distributor thing is wrong about where it thinks tdc is?


That was my thinking.

Is the timing set to 9deg on the flywheel at idle as that is where the map starts
_________________
1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 2008
Location: Somerset, UK

PostPosted: Fri Sep 04, 2020 5:16 am    Post subject: Reply with quote

Check the rotor in the dizzy is not wobbling. I found a couple that did this and caused misfires at higher rpm as the rotor hit the contacts in the cap.
_________________
1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252
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