Won't start when hot debug
06-02-2018, 09:44 PM
#1
Rennlist Member
Thread Starter
Won't start when hot debug
This problem has quickly evolved into a complete no-start when engine has been run longer and everything (including fuel system) is hot. 4 hours before cool enough to re-start. If I re-start within the first few minutes after long hot run, starts fine. If I wait 10 mins or more...4 hours.
So, reading other threads it sounds like the problem is 99% a CIS fuel pressure/boiling/vapor lock issue. Based on that, and the car's circumstance (34K miles, parked the last 10 years, fuel pumps and filter recently replaced) in what order would your best guess say I should replace:
- Warm up regulator
- Check valve
- Fuel accumulator
And what else?
So, reading other threads it sounds like the problem is 99% a CIS fuel pressure/boiling/vapor lock issue. Based on that, and the car's circumstance (34K miles, parked the last 10 years, fuel pumps and filter recently replaced) in what order would your best guess say I should replace:
- Warm up regulator
- Check valve
- Fuel accumulator
And what else?
06-03-2018, 12:57 AM
#2
Rennlist Member
Fuel accumulator for sure
06-03-2018, 01:18 AM
#3
Burning Brakes
First thing is hook up fuel pressure gauges so you can see if the system holds pressure. The manuals will tell you (sorry don’t know offhand) what residual pressure should be after x minutes, I believe.
But my first thought is accumulator and check valve.
I see no reason to get a new WUR, but I strongly suggest having it made adjustable so you can fine tune (in CIS standards) the car.
Always keep in mind the 3 most important things in terms of CIS working properly. In this order:
1. Fuel Pressure
2. Fuel Pressure
3. Fuel Pressure
i doubt its vapor lock. I just don’t hear about that much on these cars - unlike the old Audi 10 valve 5 cylinder turbo motors. Loved that motor but notorious for vapor locking.
Brandon
But my first thought is accumulator and check valve.
I see no reason to get a new WUR, but I strongly suggest having it made adjustable so you can fine tune (in CIS standards) the car.
Always keep in mind the 3 most important things in terms of CIS working properly. In this order:
1. Fuel Pressure
2. Fuel Pressure
3. Fuel Pressure
i doubt its vapor lock. I just don’t hear about that much on these cars - unlike the old Audi 10 valve 5 cylinder turbo motors. Loved that motor but notorious for vapor locking.
Brandon
06-03-2018, 08:41 AM
#4
Rennlist Member
First thing is hook up fuel pressure gauges so you can see if the system holds pressure. The manuals will tell you (sorry don’t know offhand) what residual pressure should be after x minutes, I believe.
But my first thought is accumulator and check valve.
I see no reason to get a new WUR, but I strongly suggest having it made adjustable so you can fine tune (in CIS standards) the car.
Always keep in mind the 3 most important things in terms of CIS working properly. In this order:
1. Fuel Pressure
2. Fuel Pressure
3. Fuel Pressure
i doubt its vapor lock. I just don’t hear about that much on these cars - unlike the old Audi 10 valve 5 cylinder turbo motors. Loved that motor but notorious for vapor locking.
Brandon
But my first thought is accumulator and check valve.
I see no reason to get a new WUR, but I strongly suggest having it made adjustable so you can fine tune (in CIS standards) the car.
Always keep in mind the 3 most important things in terms of CIS working properly. In this order:
1. Fuel Pressure
2. Fuel Pressure
3. Fuel Pressure
i doubt its vapor lock. I just don’t hear about that much on these cars - unlike the old Audi 10 valve 5 cylinder turbo motors. Loved that motor but notorious for vapor locking.
Brandon
Minimum pressure after 20 minutes - 1.4 bar
Brandon, you doubt it's vapor lock? That's exactly what is happening here. Wicks states that the car won't start after a 10 minute heat soak. If it were the WUR, the car wouldn't run at all.
Hard or no starting after heat soak is frequently caused by a faulty accumulator.
06-03-2018, 01:11 PM
#5
Rennlist Member
Thread Starter
Thanks muchly - I'm going to replace the accumulator and check valve while I'm in there. As well as plugs, cap/rotor and such, and maybe tackle the valve adjust and possibly pull the injectors to go for clean/flow.
What else should I clean/check/replace/adjust while I have the cooler off and such?
Do soft fuel lines go bad causing pressure issues? (a frequent issue on the old MFI cars)
- check vacuum lines
- pressure relief valve?
- ?
- ?
What else should I clean/check/replace/adjust while I have the cooler off and such?
Do soft fuel lines go bad causing pressure issues? (a frequent issue on the old MFI cars)
- check vacuum lines
- pressure relief valve?
- ?
- ?
06-04-2018, 01:31 PM
#6
Burning Brakes
Minimum pressure after 10 minutes - 1.6 bar
Minimum pressure after 20 minutes - 1.4 bar
Brandon, you doubt it's vapor lock? That's exactly what is happening here. Wicks states that the car won't start after a 10 minute heat soak. If it were the WUR, the car wouldn't run at all.
Hard or no starting after heat soak is frequently caused by a faulty accumulator.
Minimum pressure after 20 minutes - 1.4 bar
Brandon, you doubt it's vapor lock? That's exactly what is happening here. Wicks states that the car won't start after a 10 minute heat soak. If it were the WUR, the car wouldn't run at all.
Hard or no starting after heat soak is frequently caused by a faulty accumulator.
Brandon
'91 911 Turbo
'00 Audi S4 highly mod'd DD
06-04-2018, 04:13 PM
#7
Rennlist Member
Thanks muchly - I'm going to replace the accumulator and check valve while I'm in there. As well as plugs, cap/rotor and such, and maybe tackle the valve adjust and possibly pull the injectors to go for clean/flow.
What else should I clean/check/replace/adjust while I have the cooler off and such?
Do soft fuel lines go bad causing pressure issues? (a frequent issue on the old MFI cars)
- check vacuum lines
- pressure relief valve?
- ?
- ?
What else should I clean/check/replace/adjust while I have the cooler off and such?
Do soft fuel lines go bad causing pressure issues? (a frequent issue on the old MFI cars)
- check vacuum lines
- pressure relief valve?
- ?
- ?
New fuel lines are expensive. A hydraulic shop could crimp new hoses on the old lines. You probably would have to supply the hose.
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06-04-2018, 09:57 PM
#9
Rennlist Member
Thread Starter
Any tips on removing the rear fuel lines from accumulator? 17mm wrench on em, won't budge. And not a lot of levering space. Front one came off by circumstantially having the special 17mm tool for old MFI pump handy. It doesn't fit around back.
Do people remove the lines from where they go rather, and drag the accumulator out with them attached? Seems tough with the hard lines.
Do people remove the lines from where they go rather, and drag the accumulator out with them attached? Seems tough with the hard lines.
06-06-2018, 02:26 PM
#13
Rennlist Member
Thnx Wicks. I saw your other thread re: Vac connections -
>>> https://rennlist.com/forums/964-turb...tion-hose.html
.. so I'll reply over there, since I just looked at my car.
Re: Distributor, I'm interested in this answer re: grease too,.. since I've never messed with mine,... so it may need it.
=Steve
>>> https://rennlist.com/forums/964-turb...tion-hose.html
.. so I'll reply over there, since I just looked at my car.
Re: Distributor, I'm interested in this answer re: grease too,.. since I've never messed with mine,... so it may need it.
=Steve
06-07-2018, 10:41 AM
#14
Rennlist Member
I'm not near my car a the moment so I can't check what I'm saying until tonight.
06-09-2018, 07:40 PM
#15
Rennlist Member
Thread Starter
Replacement of Accumulator solved this issue. Thanks Helio and all. Stragely, I have a little bit of dieseling now, which I can live with. Still more tune-up work to do.