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Gbuckner
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Joined: November 23, 2012
Posts: 12
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 Posted: Sun Sep 24, 2017 9:13 pm Post subject: Van will not start unless I unplug the Air Flow Meter. |
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1990 Vanagon. Van will not start unless I unplug the Air Flow Meter. It will start right up and rev to 2,500 RPMs, as soon as I plug in the AFM it stalls. I replaced the AFM with a rebuilt one, no change! HELP!
Any suggestions on where I should start my diagnostics? |
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djkeev
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Joined: September 30, 2007
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Location: Reading Pennsylvania
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Gbuckner
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Joined: November 23, 2012
Posts: 12
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| Posted: Mon Sep 25, 2017 3:43 am Post subject: Re: Van will not start unless I unplug the Air Flow Meter. |
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| Sorry . . . The van I'm having trouble with is a 1990 Vanagon "Westy" 2.1 Automatic. |
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bizarre
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Joined: July 29, 2016
Posts: 54
Location: Sydney
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| Posted: Tue Sep 26, 2017 4:36 am Post subject: Re: Van will not start unless I unplug the Air Flow Meter. |
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Any damage to the plug or wiring?
Are you certain the "rebuilt" AFM works?
Has this van ever worked or is it a project you have acquired? |
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Gbuckner
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Joined: November 23, 2012
Posts: 12
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| Posted: Tue Sep 26, 2017 1:52 pm Post subject: Re: Van will not start unless I unplug the Air Flow Meter. |
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Bizarre,
I checked the continuity from the AFM plug back to the Electronic Control Unit. All is good there.
I believe the rebuilt AFM is good. I did the continuity checks recommended by Bentley on the rebuilt AFM. It passed the test.
I've had the van for 17 years. It always needs a bit of work, but is has run consistently for those 17 years.
Thanks for your inquiry. |
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Vanagon Nut
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Joined: February 08, 2008
Posts: 10379
Location: Sunshine Coast B.C.
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| Posted: Tue Sep 26, 2017 2:13 pm Post subject: Re: Van will not start unless I unplug the Air Flow Meter. |
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| Gbuckner wrote: |
| 1990 Vanagon. Van will not start unless I unplug the Air Flow Meter. It will start right up and rev to 2,500 RPMs, as soon as I plug in the AFM it stalls. ........ |
Vacuum leak?
edit: wasn't going to include this as I don't want you to chase the wrong thing or introduce more variables, but it's easy to disconnect the idle control module, block off the ICV hose and hole at intake boot, turn big screw on throttle body all the way in (seat it gently, count full turns) then turn it out about 2-3 full turns. The 2500 RPM thing seems odd. Any time I've inadvertently left the AFM unplugged, the engine runs like crap with a low idle.
Neil.
_________________
1981 Westy DIY 15º ABA
1988 West DIY 50º ABA
VE7TBN |
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Gbuckner
Samba Member
Joined: November 23, 2012
Posts: 12
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| Posted: Tue Sep 26, 2017 2:56 pm Post subject: Re: Van will not start unless I unplug the Air Flow Meter. |
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| Vanagon Nut wrote: |
| Gbuckner wrote: |
| 1990 Vanagon. Van will not start unless I unplug the Air Flow Meter. It will start right up and rev to 2,500 RPMs, as soon as I plug in the AFM it stalls. ........ |
Vacuum leak?
edit: wasn't going to include this as I don't want you to chase the wrong thing or introduce more variables, but it's easy to disconnect the idle control module, block off the ICV hose and hole at intake boot, turn big screw on throttle body all the way in (seat it gently, count full turns) then turn it out about 2-3 full turns. The 2500 RPM thing seems odd. Any time I've inadvertently left the AFM unplugged, the engine runs like crap with a low idle.
Neil. |
Neil,
Is this a way to check for a vacuum leak?
The van's idle RPMs were running fine before this new problem.
If this is not a way to check for a vacuum leak, how do you check? |
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Vanagon Nut
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Joined: February 08, 2008
Posts: 10379
Location: Sunshine Coast B.C.
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| Posted: Tue Sep 26, 2017 3:04 pm Post subject: Re: Van will not start unless I unplug the Air Flow Meter. |
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I'm sure helpful info regarding methods for checking are here in the forum already but were it me, I'd start with visually inspecting all hoses involved with the intake. e.g. the rubber elbow boot between the AFM and throttle body. Also, there is a small sort of "T" hose between the intake plenum and the idle control valve outlet. The small branch of that "T", where it connects to the hose, can crack open.
Neil.
_________________
1981 Westy DIY 15º ABA
1988 West DIY 50º ABA
VE7TBN |
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Phaedrus
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Posts: 500
Location: Washington
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| Posted: Tue Sep 26, 2017 8:08 pm Post subject: Re: Van will not start unless I unplug the Air Flow Meter. |
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Let's try to separate an electrical issue from intake. When you say "it doesn't start," does it try to fire, or just cranks endlessly? If it tries to fire and just can't catch hold, could be air. If it cranks but no fire, I'd be checking my case grounds. It'd have to be a pretty massive intake leak for the van to not want to start at all, not a little vac hose... When it starts without the AFM connected, does it hold idle at normal speed, or does it hang and stutter, wanting to die or rev?
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1986 WBX (Tin Top Camper) |
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Vanagon Nut
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Location: Sunshine Coast B.C.
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| Posted: Tue Sep 26, 2017 8:52 pm Post subject: Re: Van will not start unless I unplug the Air Flow Meter. |
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| Phaedrus wrote: |
| ....When you say "it doesn't start," does it try to fire, or just cranks endlessly? If it tries to fire and just can't catch hold, could be air. .... When it starts without the AFM connected, does it hold idle at normal speed, or does it hang and stutter, wanting to die or rev? |
| Gbuckner wrote: |
| Van will not start unless I unplug the Air Flow Meter. It will start right up and rev to 2,500 RPMs, as soon as I plug in the AFM it stalls. |
The OP indicates that his engine revs to 2500 RPM with AFM disconnected. Based upon what he wrote, it only starts if AFM disconnected. But yes, does it stay running?
Neil.
_________________
1981 Westy DIY 15º ABA
1988 West DIY 50º ABA
VE7TBN |
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djkeev
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Joined: September 30, 2007
Posts: 32632
Location: Reading Pennsylvania
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Gbuckner
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Joined: November 23, 2012
Posts: 12
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| Posted: Wed Sep 27, 2017 3:35 am Post subject: Re: Van will not start unless I unplug the Air Flow Meter. |
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| Phaedrus wrote: |
| Let's try to separate an electrical issue from intake. When you say "it doesn't start," does it try to fire, or just cranks endlessly? If it tries to fire and just can't catch hold, could be air. If it cranks but no fire, I'd be checking my case grounds. It'd have to be a pretty massive intake leak for the van to not want to start at all, not a little vac hose... When it starts without the AFM connected, does it hold idle at normal speed, or does it hang and stutter, wanting to die or rev? |
Phaedrus,
With the AFM plugged in it will fire and start for a split second, then dies.
With AFM unplugged it starts immediately, revs to 2,500 RPMs and stays running at 2,500 RPMs. |
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djkeev
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JudoJeff
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Joined: May 24, 2013
Posts: 1179
Location: Near Springfield, MA
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| Posted: Wed Sep 27, 2017 5:01 am Post subject: Re: Van will not start unless I unplug the Air Flow Meter. |
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My bet is on bad ecu.
Dave, you brought back memories.....
_________________
________________________________________
1989 Vanagon GL Westfalia Camper, Burned up on 7/31/16.
1987 Vanagon GL Westfalia Camper, Bostig & Rebuilt, sold
1986 Vanagon GL Westfalia Camper, Bostig Sold May 10, 2021
1999 Ford GTRV Westfalia camper (30% bigger Westy layout) |
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Nuthin2It 
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Joined: December 31, 2011
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Location: Marietta, GA
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| Posted: Wed Sep 27, 2017 5:13 am Post subject: Re: Van will not start unless I unplug the Air Flow Meter. |
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What have you checked so far? Check the easy things first. Does each spark plug fire? You can tell a lot from the color and deposits on the plugs. Compare all four of them. Are the fuel injectors spraying fuel in a mist?
I have a 1.9 liter so it may not apply, but when I forgot to plug in the AFM the engine ran at high RPM also.
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1985 Westfalia 15 degree EA288 Boxeer |
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djkeev
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shagginwagon83
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Joined: February 07, 2016
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| Posted: Wed Sep 27, 2017 6:19 am Post subject: Re: Van will not start unless I unplug the Air Flow Meter. |
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I had starting issues on my 83.5. My mechanic could not figure it out - after having the van for a month. He thought it was the ECU. Replaced it - no difference.
I thought it could be the timing - so I followed the instructions in the Bentley. Before I started, I tried to start the van - nothing. First step was to bypass the Idle Control Unit. I bypassed it, took the unit off, and heard things rattling inside. I tried to start the van - started right up! This is like 10 minutes after I tried to get the van to start. Turned it off, then back on - right up.
Hundreds of dollars spent on replacing older working parts (coil, fuel pump, injectors, etc) and it was a $30 part from Van Cafe. Here is some blown capacitors inside my unit. Here is a snapchat of the unit. the yellow ceramic capacitors were toasted.
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Brandon
"Jo Ann" - '83.5 Westfalia EJ22e w/Peloquin
Instagram @joannthevan |
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Vanagon Nut
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Location: Sunshine Coast B.C.
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| Posted: Wed Sep 27, 2017 2:08 pm Post subject: Re: Van will not start unless I unplug the Air Flow Meter. |
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| shagginwagon83 wrote: |
I thought it could be the timing - so I followed the instructions in the Bentley. Before I started, I tried to start the van - nothing. First step was to bypass the Idle Control Unit. I bypassed it, took the unit off, and heard things rattling inside. I tried to start the van - started right up! This is like 10 minutes after I tried to get the van to start. Turned it off, then back on - right up.
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Though designed differently, with Digijet or Digifant, if the idle control system is properly disabled-bypassed, the engine should run ok. PS/AC loads notwithstanding, idle may need to be adjusted.
Looking at 1990 wiring diagram in Bentley, ICU 8/LS red/blue wire connects to ECU 11. A second wire from ECU 11 runs to the throttle switch. The other side of that switch connects to 94 ground junction in harness. In part, this junction supplies a ground to AFM pin 4. IF the ICU, an involved component or wire(s) was faulty, would that cause the idle control valve to work incorrectly? e.g. connecting the AFM would incorrectly cause the valve to allow too little air through? DISconnected the AFM would incorrectly cause the valve to allow too much air into the intake plenum?
Neil.
edited for clarity.
_________________
1981 Westy DIY 15º ABA
1988 West DIY 50º ABA
VE7TBN |
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Gbuckner
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Joined: November 23, 2012
Posts: 12
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| Posted: Wed Sep 27, 2017 5:16 pm Post subject: Re: Van will not start unless I unplug the Air Flow Meter. |
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Okay. Based on the advice thus far my strategy for this weekend will be:
1) as per Neil (Vanagon Nut) check all hoses involved with the intake.
2) as per Shagginwagon83 inspect the Idle Control Unit (ICU). Any advice on how to check the ICU?
Further, I am very interested in Neil's (Vanagon Nut) musings (see below) on the wiring between the ICU, ECU and the AFM. Neil if you could explain how I might check your theory I would be eternally grateful.
" . . ICU 8/LS red/blue wire connects to ECU 11. A second wire from ECU 11 runs to the throttle switch. The other side of that switch connects to 94 ground junction in harness. In part, this junction supplies a ground to AFM pin 4. IF the ICU, an involved component or wire(s) was faulty, would that cause the idle control valve to work incorrectly? e.g. connecting the AFM would incorrectly cause the valve to allow too little air through? DISconnected the AFM would incorrectly cause the valve to allow too much air into the intake plenum?" |
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Vanagon Nut
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Joined: February 08, 2008
Posts: 10379
Location: Sunshine Coast B.C.
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| Posted: Wed Sep 27, 2017 7:43 pm Post subject: Re: Van will not start unless I unplug the Air Flow Meter. |
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| Gbuckner wrote: |
2) as per Shagginwagon83 inspect the Idle Control Unit (ICU). Any advice on how to check the ICU?
Further, I am very interested in Neil's (Vanagon Nut) musings (see below) on the wiring between the ICU, ECU and the AFM. Neil if you could explain how I might check your theory I would be eternally grateful.
" . . ICU 8/LS red/blue wire connects to ECU 11. A second wire from ECU 11 runs to the throttle switch. The other side of that switch connects to 94 ground junction in harness. In part, this junction supplies a ground to AFM pin 4. IF the ICU, an involved component or wire(s) was faulty, would that cause the idle control valve to work incorrectly? e.g. connecting the AFM would incorrectly cause the valve to allow too little air through? DISconnected the AFM would incorrectly cause the valve to allow too much air into the intake plenum?" |
| Vanagon Nut wrote: |
........
edit: ....... it's easy to disconnect the idle control module, block off the ICV hose and hole at intake boot, turn big screw on throttle body all the way in (seat it gently, count full turns) then turn it out about 2-3 full turns.
..... |
Once vacuum leaks are ruled out, disconnect the ICU and plug off those holes, adjust idle screw accordingly. (you'd likely need to back it out from where it was when van ran ok) See what happens with AFM connected or disconnected. If no change, then I'd think that the issue doesn't lay at the idle control valve.
As for checking out any wiring issues, it's taking me too long to study the diagrams and transfer what I *think* one could do (continuity checks between ECU connector and various other points in harnesses). I don't mean that negatively and I'm not dodging doing the work.  Just want to wait till you do the vacuum checks then see how it runs with the IC system disconnected etc.
In terms of checking the ICU itself, if you search ICU here, you will find way more information than I can provide (e.g. I recall a thread about transistor replacement replete with part numbers) but would suggest that if somethings wrong with it, it will typically show up on a visual inspection. Like shaggin shows. Look for obvious burned or broken components, etc. The connections at that ICU can get corroded too. And, given its location, it wouldn't be far fetched for moisture to get inside the ICU itself.
There's been a lot written here by folks more knowledgable than me. Not saying you haven't but if you search around here, you can pick up a lot of good information.
Neil.
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1981 Westy DIY 15º ABA
1988 West DIY 50º ABA
VE7TBN |
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