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myvanrunsonrainbows
Samba Member
Joined: February 12, 2020
Posts: 38
Location: Grass Valley, CA
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 Posted: Thu Apr 01, 2021 7:51 pm Post subject: Fuel pump relay puzzle (only starts after bypassing) [1980AC] |
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Hello Sambites, I have a ignition/fuel relay puzzle that has got me stumped.
My 1980 aircooled vanagon (BusDepot 2.0L with ~4000 miles on it), Buttercup, has an intermittent starting issue that I have traced back to something with the fuel pump relay. Here's the symptoms
20-30% of the time (more often when its cold), Buttercup will start, turn over a few times, and then die - and are only two things I've found that will start her back up again.
The first is a roll start. Like, a looong roll start. I first figured this out while forlornly getting rope-towed down a county road by a beat up chevy, during which I decided to try pop starting it. It took about a hundred feet before she sputtered to life, but I made it home on my own two liters. I was able to repeat this several times over the next few months, and was always sure to camp on hills with a nice long runway in front of me.
While researching possible causes, I came across this thread, detailing a wiring bypass tool that can be used to diagnose fuel ignition issues: [https://www.thesamba.com/vw/forum/viewtopic.php?t=349429]
I built the rig exactly as described (including fuse and diode), and sure enough, when I unplugged my fuel pump relay and plugged the bypass wire into leg 87 and the ignition coil, she started right up.
BUT she doesnt keep running. She'll run for about 10 seconds like this, and then sputter and die. Well, the good news, is if I then plug everything back in normally (remove the bypass wire, replug the wires back into the fuel relay), she started and runs perfectly. EVERY SINGLE TIME.
Through an organic process of elimination (read: one of my spade terminals broke, and I was in a desperate situation), I figured out that I only actually need to plug the spade into one side of my fuel pump relay terminal sockets. The one that connects to the fuel pump/ECU, and runs the fuel pump when powered.
This allows the van to start. It dies 10 seconds later, and then it starts up normally (with everything plugged back in) - EVERY SINGLE TIME.
I've gotten way faster at this bootleg start than I care to admit, because 1 out of every 3 times I get in the van to start it, I end up jumping this relay and getting it started that way.
I'm stumped.
Any ideas?
Recent replacements:
Fuel pump
Fuel filter
All fuel lines
Injectors cleaned and tested
New vacuum lines
New fuel pump relay
TLDR
Van wont start sometimes unless I 1) roll start it or 2) connect a wire directly from my battery to terminal 87 of fuel pump/ECU harness (left side of the relay). When I do that, it starts, then stalls, and then starts normally (if I plug everything back in), 100% of the time.[/url] |
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myvanrunsonrainbows
Samba Member
Joined: February 12, 2020
Posts: 38
Location: Grass Valley, CA
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| Posted: Thu Apr 01, 2021 8:06 pm Post subject: Re: Fuel pump relay puzzle (only starts after bypassing) [1980AC] |
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obligatory unrelated picture
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danfromsyr
Samba Member
Joined: March 01, 2004
Posts: 15144
Location: Syracuse, NY
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| Posted: Thu Apr 01, 2021 8:18 pm Post subject: Re: Fuel pump relay puzzle (only starts after bypassing) [1980AC] |
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TLDR sorry it's late, but one thing that we had on our 1980 at times was the contacts inside the AFM (under the plastic cover)
when you start the engine, the fuel pump is 1st energized by the KEY in the Crank position. it gets a power feed from the starter circuit.
then inside the AFM is a set of contact points that make contact when the engine is sucking air.. and it's these points that must stay in contact to operate the fuel pump from then on..
so ours were weak and weren't holding a constant contact to keep the fuel pump relay triggered.
similar issues can be inside the fuel pump relay, they do age and loose contact at times.
not sure if this helps, but maybe helps understand what's supposed to happen, if it all happens correctly.
best luck.
edit: Ps that's a lovely pic.. thanks for sharing..
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myvanrunsonrainbows
Samba Member
Joined: February 12, 2020
Posts: 38
Location: Grass Valley, CA
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| Posted: Mon Apr 05, 2021 10:11 am Post subject: Re: Fuel pump relay puzzle (only starts after bypassing) [1980AC] |
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Bump for visibility - anyone else experienced this issue?
You have my word that I will solve this issue once and for all (and share the solution here).
In the meantime, had a great weekend trip on the North Yuba. No issues to report.
Check out Carlton Campground near Downieville CA for some beautiful (easily accessible) camping right by the river.
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Vanagon Nut
Samba Member
Joined: February 08, 2008
Posts: 10379
Location: Sunshine Coast B.C.
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| Posted: Mon Apr 05, 2021 10:52 am Post subject: Re: Fuel pump relay puzzle (only starts after bypassing) [1980AC] |
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The AFC 'pro manual' pdf can be found online. It will help!
I see your "100% of the time" comment but....
engine up to temp, after starting engine using fuel pump bypass method, does engine stay running? Even if answer is "yes".....
My gut tells me that there's something in parts involved in cold start affecting the initial run after engine starts.
With the fuel pump relay plugs disconnected and wiring bypassed to run the pump, it appears the "therm time switch", "aux air reg", "cold start valve" P 97.13 Bentley would not operate (be connected). Those parts not functioning would certainly affect how the engine runs especially when cold.
I'd suggest doing a fuel system pressure and delivery volume tests.
Neil.
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1981 Westy DIY 15º ABA
1988 West DIY 50º ABA
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MarkWard
Samba Member
Joined: February 09, 2005
Posts: 17153
Location: Retired South Florida
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| Posted: Mon Apr 05, 2021 11:12 am Post subject: Re: Fuel pump relay puzzle (only starts after bypassing) [1980AC] |
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When the engine is cold, it could be starting off the cold start valve/ 5th injector. Energizing the fuel pump pressurizes the injector. It sprays the plenum as if you were spraying fuel directly in the intake. As described the air flow sensor takes over pump operation once the engine starts.
You need to verify if the other injectors are working when it won’t start.
Pull starting and relay jumping tells you the engine is sound, but actual troubleshooting requires everything to be connected as intended and then to determine what isn’t functioning.
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myvanrunsonrainbows
Samba Member
Joined: February 12, 2020
Posts: 38
Location: Grass Valley, CA
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| Posted: Tue Apr 06, 2021 4:51 pm Post subject: Re: Fuel pump relay puzzle (only starts after bypassing) [1980AC] |
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| Vanagon Nut wrote: |
The AFC 'pro manual' pdf can be found online. It will help!
I see your "100% of the time" comment but....
engine up to temp, after starting engine using fuel pump bypass method, does engine stay running? Even if answer is "yes".....
My gut tells me that there's something in parts involved in cold start affecting the initial run after engine starts.
With the fuel pump relay plugs disconnected and wiring bypassed to run the pump, it appears the "therm time switch", "aux air reg", "cold start valve" P 97.13 Bentley would not operate (be connected). Those parts not functioning would certainly affect how the engine runs especially when cold.
I'd suggest doing a fuel system pressure and delivery volume tests.
Neil. |
Hi Neil, thank you for the response! You might be on to something. The issue occurs much more frequently when the engine is cold (early morning starts), and much less frequently once the engine is 'at temp'. But, this isn't a 100% rule, as I have had it happen once or twice when the engine is fully warmed up. I also have been trying to figure out the relationship between the cold start valve, and my starting issue.
When it's cold, I turn the key, and I hear what I think is the cold start valve firing before the engine turns over. Maybe 3-5 seconds of a 'whirring' sound followed by the engine turning over. It often then sputters and dies. If I'm understanding you correctly, this could be caused by my injectors not firing, so it starts off the the gas injected by the cold start, but then dies.
I've tested my fuel pressure at the relief valve with the following results:
28-30 psi at idle.
No change at ~3000 rpm.
Removed vacuum hose.
36-38 psi
Still no change at 3000 rpm.
I believe my fuel pressure is supposed to increase with RPM, right?
Maybe a faulty FPR?
I'll look into doing a fuel delivery test.
It seems like this issue only happens when I'm in a hurry to get somewhere, and rarely when I have the time to investigate |
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myvanrunsonrainbows
Samba Member
Joined: February 12, 2020
Posts: 38
Location: Grass Valley, CA
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| Posted: Tue Apr 06, 2021 4:54 pm Post subject: Re: Fuel pump relay puzzle (only starts after bypassing) [1980AC] |
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| MarkWard wrote: |
When the engine is cold, it could be starting off the cold start valve/ 5th injector. Energizing the fuel pump pressurizes the injector. It sprays the plenum as if you were spraying fuel directly in the intake. As described the air flow sensor takes over pump operation once the engine starts.
You need to verify if the other injectors are working when it won’t start.
Pull starting and relay jumping tells you the engine is sound, but actual troubleshooting requires everything to be connected as intended and then to determine what isn’t functioning. |
Thanks for the response Mark!
How would you recommend testing the injectors?
I think you could be right about the cold start valve allowing it to start, but then dying.
I had my injectors professionally cleaned and test recently, so I doubt it's them, but maybe an issue with the ECU not telling them to fire? |
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MarkWard
Samba Member
Joined: February 09, 2005
Posts: 17153
Location: Retired South Florida
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| Posted: Tue Apr 06, 2021 5:06 pm Post subject: Re: Fuel pump relay puzzle (only starts after bypassing) [1980AC] |
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You can remove the injectors from one side and visually see if they are spraying. Be careful you don’t spark a fire. Best to remove the coil wire from the distributor cap and ground it.
It’s easier to unplug an injector and test it with a noid light or even listen with a stethoscope. The injector should click as the engine cranks.
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Vanagon Nut
Samba Member
Joined: February 08, 2008
Posts: 10379
Location: Sunshine Coast B.C.
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| Posted: Wed Apr 07, 2021 10:00 am Post subject: Re: Fuel pump relay puzzle (only starts after bypassing) [1980AC] |
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| myvanrunsonrainbows wrote: |
| Vanagon Nut wrote: |
The AFC 'pro manual' pdf can be found online.
engine up to temp, after starting engine using fuel pump bypass method, does engine stay running? Even if answer is "yes".....
My gut tells me that there's something in parts involved in cold start affecting the initial run after engine starts.
With the fuel pump relay plugs disconnected and wiring bypassed to run the pump, it appears the "therm time switch", "aux air reg", "cold start valve" P 97.13 Bentley would not operate (be connected). Those parts not functioning would certainly affect how the engine runs especially when cold.
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The issue occurs much more frequently when the engine is cold (early morning starts), and much less frequently once the engine is 'at temp'. But, this isn't a 100% rule, as I have had it happen once or twice when the engine is fully warmed up. I also have been trying to figure out the relationship between the cold start valve, and my starting issue.
When it's cold, I turn the key, and I hear what I think is the cold start valve firing before the engine turns over. Maybe 3-5 seconds of a 'whirring' sound followed by the engine turning over. It often then sputters and dies. If I'm understanding you correctly, this could be caused by my injectors not firing, so it starts off the the gas injected by the cold start, but then dies.
I've tested my fuel pressure at the relief valve with the following results:
28-30 psi at idle.
No change at ~3000 rpm.
Removed vacuum hose.
36-38 psi
Still no change at 3000 rpm.
I believe my fuel pressure is supposed to increase with RPM, right?
Maybe a faulty FPR? |
Was the start/run issue happening before engine replacement?
A quick and easy test for fuel pressure regulator. Gently suck on vacuum hose. You should not be able to pull air through. If it's ok, I'd ignore the FPR for now.
It sounds like you hear the whirring sound when key is turned to ignition on only. If so, that sound is likely coming from the fuel pump. Thats normal.
Bentley shows specs for fuel pressure and the later editions has parts descriptions including info on the FPR.
Other parts work in conjunction with the cold start valve. e.g. thermo time switch and aux air valve.
File name of AFC manual I found online:
AFC_FI_Training_Troubleshooting_Manual
I wasn't suggesting that the cold start valve itself is the issue. And, even IF all the injectors weren't operating, I doubt the CSV could supply enough fuel for engine to run briefly. Fire, maybe, run, no.
Your engine may have more than one factor causing the issue(s) you see. As a matter of course, cleaning electrical grounds can't hurt. i.e. engine replacement is no guarantee that grounds were cleaned and/or repaired during that process. And, old wires, connectors that get disturbed during an engine R&R could reveal a fault after engine install.
Neil.
_________________
1981 Westy DIY 15º ABA
1988 West DIY 50º ABA
VE7TBN |
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MarkWard
Samba Member
Joined: February 09, 2005
Posts: 17153
Location: Retired South Florida
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| Posted: Wed Apr 07, 2021 10:47 am Post subject: Re: Fuel pump relay puzzle (only starts after bypassing) [1980AC] |
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If you have the factory manual, I'd look at pages 97.12 and .13 Specifically 97.13. It pictures what is labeled Fuel pump relay, but it's known as the double relay. It is very important and can go bad. I'm assuming that is where you are doing your jumping?
Key on, you should have 12 volts at 86c of the relay board. Cranking you should have 12 volts at 86a. This relay powers the ECU and the fuel pump.
edit, it's not shown, but some relays had an external ground wire that was under the screw that holds the relay to the van. The metal case relay grounded through the case. At some point the relay got a plastic case and needed the ground.
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myvanrunsonrainbows
Samba Member
Joined: February 12, 2020
Posts: 38
Location: Grass Valley, CA
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| Posted: Mon Apr 12, 2021 1:29 pm Post subject: Re: Fuel pump relay puzzle (only starts after bypassing) [1980AC] |
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[quote="Vanagon Nut"]
| myvanrunsonrainbows wrote: |
Was the start/run issue happening before engine replacement?
A quick and easy test for fuel pressure regulator. Gently suck on vacuum hose. You should not be able to pull air through. If it's ok, I'd ignore the FPR for now.
It sounds like you hear the whirring sound when key is turned to ignition on only. If so, that sound is likely coming from the fuel pump. Thats normal.
Bentley shows specs for fuel pressure and the later editions has parts descriptions including info on the FPR.
Other parts work in conjunction with the cold start valve. e.g. thermo time switch and aux air valve.
File name of AFC manual I found online:
AFC_FI_Training_Troubleshooting_Manual
I wasn't suggesting that the cold start valve itself is the issue. And, even IF all the injectors weren't operating, I doubt the CSV could supply enough fuel for engine to run briefly. Fire, maybe, run, no.
Your engine may have more than one factor causing the issue(s) you see. As a matter of course, cleaning electrical grounds can't hurt. i.e. engine replacement is no guarantee that grounds were cleaned and/or repaired during that process. And, old wires, connectors that get disturbed during an engine R&R could reveal a fault after engine install.
Neil. |
Hi Vanagon Nut, thanks for the response!
Unfortunately, I dont know if the issue was happening before, as I inherited the van with 2x blown heads, and it hadnt been driven in about 4 years. It was my grandmas daily driver beforehand, so I dont think she was having this issue, but it sat for awhile before she gave it to me.
I will do that FPR test tonight and get back to you!
With regards to the starting/fuel pump sequence, the whirring noise I hear only happens when I turn the key to the 'start' position, and occurs for 3-5 seconds before the engine begins to turn over. It only does this when it is cold out/starting the engine cold, which leads me to believe that it is the cold start valve or thermotime switch. When the engine is warm, the engine cranks immediately with no whirring sound.
I have tested this at my fuel pump and confirmed that my pump only gets juice when cranking the engine, not when the key is 'on'.
Is this normal? |
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myvanrunsonrainbows
Samba Member
Joined: February 12, 2020
Posts: 38
Location: Grass Valley, CA
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| Posted: Mon Apr 12, 2021 1:32 pm Post subject: Re: Fuel pump relay puzzle (only starts after bypassing) [1980AC] |
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| MarkWard wrote: |
If you have the factory manual, I'd look at pages 97.12 and .13 Specifically 97.13. It pictures what is labeled Fuel pump relay, but it's known as the double relay. It is very important and can go bad. I'm assuming that is where you are doing your jumping?
Key on, you should have 12 volts at 86c of the relay board. Cranking you should have 12 volts at 86a. This relay powers the ECU and the fuel pump.
edit, it's not shown, but some relays had an external ground wire that was under the screw that holds the relay to the van. The metal case relay grounded through the case. At some point the relay got a plastic case and needed the ground. |
Thank you Mark, I will look that up!
I have the Bentley, and have tried to interpret the wiring diagrams, but struggled with them. I have some electrical engineering background (I can read single line / 3 line diagrams), but I find the Bentley diagrams extremely confusing. Do you know of any good resources for teaching how to read them?
There is a +12v permanent jumper between two of the terminals on my relay plug, and I cant figure out if it is supposed to be there. (I'm at work now, i can post the terminal numbers later). |
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MarkWard
Samba Member
Joined: February 09, 2005
Posts: 17153
Location: Retired South Florida
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| Posted: Mon Apr 12, 2021 2:49 pm Post subject: Re: Fuel pump relay puzzle (only starts after bypassing) [1980AC] |
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The manual at the front of the diagrams has a tutorial. It’s actually a very simple layout. What is missing is the drawing of the vehicle under it. Basically the bottom of the page is grounds. The top of the page is the fuse box. The numbers along the bottom are current tracks. Switches are shown at rest as well as the relays.
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