Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > 911 / 930 Turbo & Super Charging Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Smart quod bastardus
 
fredmeister's Avatar
 
Join Date: Oct 2002
Location: Baltimore, MD, USA
Posts: 2,235
Garage
need help with engine misfire

I installed an MSD 6AL2 programmable ignition and am having a terrible misfire after the engine has started.

The rotor is the NAPA non resistor rotor and brand new cap. Wires are stock OEM braidied wires and the plugs were gapped at 0.040.

I am able to start the car and it runs fine for the first 1 minute or two then it starts to stumble and misfire. As soon as I touch the gas peddle to rev it up the engine starts to backfire and stall. AF ratio is bouncing all over the place going lean then rich as this is happening.

My max timing was set at 32 degrees BTDC and I have programmed the retards to take out timing to exactly simulate the stock 79 turbo timing curves from the manual. Idle timing is 2 degrees BTDC at 950 rpm.

I have replaced the front fuel pump and all the relays thinking it migh be fuel related. Front pump was making some noise so I installed a Bosch 044 front pump and rewired the fuses to break up the circuit to each relay. --No change.

Fuel pressures are 3.5bar warm CP and SP is 6.4bar all within spec.

I have read on the MSD forums about rotor phasing thinking this might be the cause, but am not sure if I am barking up the wrong tree here.
HAS ANYONE HAD ISSUES WITH ROTOR PHASING WHEN USING THE MSD 6AL2 UNIT? Is this what it sounds like, as I am running out of hair to pull out of my head and need to get this thing running.

Any help is greatly appreciated from you guys this has me stumped now.

Fred

__________________
1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"
Old 05-19-2013, 01:40 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
beancounter
 
jwasbury's Avatar
 
Join Date: Jan 2008
Location: Weehawken, NJ
Posts: 3,609
Sorry to hear of these troubles Fred. That really blows. Can you swap out the MSD box for a stock CDI unit to see if the problem goes away? Just a thought as it may help to narrow things down.
__________________
Jacob
Current: 1983 911 GT4 Race Car / 1999 Spec Miata / 2000 MB SL500 / 1998 MB E300TD / 1998 BMW R1100RT / 2016 KTM Duke 690
Past: 2009 997 Turbo Cab / 1979 930
Old 05-19-2013, 04:20 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Smart quod bastardus
 
fredmeister's Avatar
 
Join Date: Oct 2002
Location: Baltimore, MD, USA
Posts: 2,235
Garage
Not really easy to do without doing major rework.

I would have to rewire the wiring harness and undo all the mods to my distributor that I made to lock it down.

Thought did cross my mind but too much time invested in the upgrade and the MSD is the unit I need to run and get it sorted.

Hopefully someone with experience with the MSD will chime in with advice.

This is so frustrating......I signed up for a track day in mid June and dont have any miles on the car yet.

Fred
__________________
1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"
Old 05-19-2013, 04:36 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
beancounter
 
jwasbury's Avatar
 
Join Date: Jan 2008
Location: Weehawken, NJ
Posts: 3,609
Maybe less work than you think. I wouldn't bother undoing your dizzy mods. You say the problem happens with the car just idling. If you wired up the MSD with a connector plug, you could make up a few jumpers to temporarily hook into the stock CDI unit. Set static timing at something reasonable (I don't know, maybe 20 BTDC) and see if your problem persists. Maybe it's this rotor phasing thing, or maybe it's a wiring problem with MSD, or maybe the MSD unit itself is wonky.
__________________
Jacob
Current: 1983 911 GT4 Race Car / 1999 Spec Miata / 2000 MB SL500 / 1998 MB E300TD / 1998 BMW R1100RT / 2016 KTM Duke 690
Past: 2009 997 Turbo Cab / 1979 930
Old 05-19-2013, 05:14 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered User
 
Join Date: Jul 2006
Location: S. Florida
Posts: 7,289
From reading your third paragraph it sounds fuel delivery related as the warm up regulator bimetallic spring heats up from cold after about a minute. Pull the 12 volt electrical plug off the WUR and see if this stuff stops for a while longer after a cold start.

It's possible your stock braided spark plug wires are German aftermarket and NFG with MSD ignition and that's causing this but if it runs OK at first after a cold start that seems less likely.
Old 05-19-2013, 06:22 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered User
 
T77911S's Avatar
 
Join Date: Oct 2006
Location: MYR S.C.
Posts: 13,433
when i installed an MSD on my 930 and fired it up, the RPM's where much higher than normal and the exhaust had a very "thin" sound with a very fast hi pitched popping.
when i checked the timing, it was VERY advanced. like around 50 degrees, maybe more. it was so far that when i rotated the dist as far as it would go, it was still past the 26 degree mark, at idle.
so i started to pull the dist and rotate the rotor to make it work. then said to myself this aint right. i should not have to do this.
i got to reading about the MSD and found the MSD wants a neg to positive trigger. i had looked at my dist output previously and saw it was pos to neg.
so even though i had it wired like the MSD said, i swapped the violet and green wire and it fired right as normal.


i am seeing that others are running just a few degress advanced at idle. i am running more than that even though i am at 26 at 4k. also, i am nearly at the end of my adjustment on the dist. i have pulled it and set it the other way but it is at the end of adjustment too.
__________________
86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:
Old 05-20-2013, 04:22 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Smart quod bastardus
 
fredmeister's Avatar
 
Join Date: Oct 2002
Location: Baltimore, MD, USA
Posts: 2,235
Garage
Well I think I may have found the issue.......yahoo!

Upon looking for fuel related causes again, I started to pull relays and fuses while the car was running. Noticed that pulling the rear relay made next to no difference idling!
1) So will the car run at idle with just the front pump?, apparently so at least for a short time.

2) Then I pulled the #6 fuse and scraped the terminal and cleaned the hell out of the fuse with sandpaper and the car started to come to life. I also pulled the brass screws out from the terminal strips and cleaned them with sandpaper and reinstalled trying to clean the connections.
When I rewired the fuel pumps last week I cut the jumper from the rear pump relay to the front pump relay and ran a separate fused lead to the front relay only. I left the rear relay alone and it still gets power from the #6 OEM fuse. Did not bother to clean the terminal strips or fuse holders since I was assuming the front pump was bad.
Turns out the rear pump was the culprit with a bad connection. It was running but apparently not enough.
Funny thing is fuel pressures were fine and stable when I tested the system with the gages and the car not running, so apparently it made pressure but not enough flow to actually run the car.

Anyway, it ran well around the parking lot and up and down the street for a mile last night before I put it away so I may be good now.

Fred
__________________
1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"
Old 05-20-2013, 06:29 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
beancounter
 
jwasbury's Avatar
 
Join Date: Jan 2008
Location: Weehawken, NJ
Posts: 3,609
Hey Fred...sounds like some good news. Fingers crossed that you've got it beat permanently.

If that pump was indeed intermittent due to wiring, perhaps it would have shown up on a fuel volume test (since the pressure seeemed ok)?
__________________
Jacob
Current: 1983 911 GT4 Race Car / 1999 Spec Miata / 2000 MB SL500 / 1998 MB E300TD / 1998 BMW R1100RT / 2016 KTM Duke 690
Past: 2009 997 Turbo Cab / 1979 930
Old 05-20-2013, 11:39 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Smart quod bastardus
 
fredmeister's Avatar
 
Join Date: Oct 2002
Location: Baltimore, MD, USA
Posts: 2,235
Garage
Quote:
Originally Posted by jwasbury View Post
Hey Fred...sounds like some good news. Fingers crossed that you've got it beat permanently.

If that pump was indeed intermittent due to wiring, perhaps it would have shown up on a fuel volume test (since the pressure seeemed ok)?
Youre right Jake, I did not bother to do a flow test because I never got that far along in the diagnosis before fixing the fuse issue.

I may still run that test just to check the condition of the rear pump. I was hoping to avoid poking around with the rear fuel lines and electrical connections at the rear pump.

Hopefully I found the problem and can get on with tuning the ignition and driving the car for awhile.

Fred

__________________
1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"
Old 05-20-2013, 06:03 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 07:36 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2020 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.