Post Reply
mats andersen
Silver
Silver
Posts: 4
Joined: Sun Jul 26, 2015 2:24 pm

Std 1986 engine stalls

Post by mats andersen »

Hi

I am new to the forum, so perhapst this issue has been raised before.
I have a well maintained 1986 2.5. It has been bulletproof for years and years.
Suddenly, like at the turn of a switch it completley dies away at 2000-2500 rpms.
Like the breath is beeing knowcked out of it so to speak. Like it suddenly doesnt get fuel or sometyhing. When warm it happens at 1500 ish. All cylinders firing.
Idle is a tiny but rougher than normal.
But it starts easily and keeps running, but not above 2500, like a rev limiter is taking action.

I first checked the fuel supply. but nothing wrong with filter or pump. Distributor cap and rotor have only done 3000kms and looks in good condition.
No black smoke when it happens.

Where to go from here? I have spent a lot of time with the 4 cyl alfettas, but not so much on the EFI V6s.

Looking forward to any clues.

Best regards

Mats Andersen
Norway
User avatar
MD
Verde
Verde
Posts: 2436
Joined: Mon Nov 22, 2004 2:37 am
Location: Brisbane, Australia
Contact:

Re: Std 1986 engine stalls

Post by MD »

A simple test to check the ignition side of things:-

Check that your coil gets a good healthy B+ and all your ground connections are sound, not corroded. Once you have done that, change your ignition coil and be sure to replace the high tension lead from the coil to the distributor as well.
Transaxle Alfas Haul More Arse
User avatar
Murray
Verde
Verde
Posts: 622
Joined: Sun Nov 28, 2004 11:16 am
Location: Lac Brome Quebec - Canada

Re: Std 1986 engine stalls

Post by Murray »

Mats
When you state " checked the fuel supply. but nothing wrong with filter or pump" does this include conducting a fuel pressure test ? What I mean by this is has a pressure gauge been inserted into the fuel line and monitored at different engine speeds/loads ? Typically you can "T" a gauge into the line and position it on the lower windshield such that you can view results while driving.This will tell you if your "dropout" is being caused by faulty - pressure regulator,pump etc.Worth a try.
1986-GTV6
1989-75 Twinspark very sadly sold-remarkable sedan !
2014 Audi Q5 3.0l TDI - torque MONSTER
kevin
Verde
Verde
Posts: 2762
Joined: Sat Jan 22, 2005 9:09 am
Location: Esher, UK

Re: Std 1986 engine stalls

Post by kevin »

I saw a GTV a few days ago where the airflow meter flap had got stuck on its pivots which created similiar problem .
Check by taking airbox off and afm cap off, then push flap with fingers to see if it rotates freely and its moving on circuit board inside afm cap .
Can also check with ignition on ( engine off) when you rotate afm by hand that fuel pump stays on while flap is wide open .
If that's all ok then do what's mentioned above and test with inline fuel pressure gauge.
Good luck .
Jim K
Verde
Verde
Posts: 1732
Joined: Tue Nov 30, 2004 12:10 am
Location: Athens,Greece

Re: Std 1986 engine stalls

Post by Jim K »

The only true way of making sure your fuel system is working ok, is to bring out a fuel pressure gauge in front of the windshield as Murray says and then also hook up an afr gauge (after welding a cheap bung on the exhaust pipe for the O2 sensor). You will be able to check afr/fuel pressure across the operating range. Chances are you'll have to tighten the afm clockspring for proper midrange afrs, as they tend to weaken over the years. Set idle afr (with the bypass screw) to 14-15.5:1, part-throttle 13.5-15:1. Top end will depend more on fuel pump capability but should be 12.7-13.5:1. If -with hot engine- you have the above values and you hear pinging on acceleration, check plug heat range and ignition advance. If you have the old V6 spring/weights distributor, there's a possibility the springs have weakened and need a bit of tightening on their posts. I prefer to set idle advance to over 10*BTDC as it makes for a livelier car, but you'd have to limit top advance at the same time by adjusting the weight travel stop pegs... My two cents worth! :wink:
Jim K.
User avatar
MD
Verde
Verde
Posts: 2436
Joined: Mon Nov 22, 2004 2:37 am
Location: Brisbane, Australia
Contact:

Re: Std 1986 engine stalls

Post by MD »

Ehrr..mats, just a small caution about JK's 2 cents worth. That Greek two cents is actually worth two slices of a gherkin given the underwater Greek economy. :wall:
Transaxle Alfas Haul More Arse
Jim K
Verde
Verde
Posts: 1732
Joined: Tue Nov 30, 2004 12:10 am
Location: Athens,Greece

Re: Std 1986 engine stalls

Post by Jim K »

I was 100% sure the phrase 'two cents' would get your attention, you cheap %$#&*! :twisted:
Jim K.
mats andersen
Silver
Silver
Posts: 4
Joined: Sun Jul 26, 2015 2:24 pm

Re: Std 1986 engine stalls

Post by mats andersen »

Hey! thanks for all the useful input. yeah actually I didnt check the actual pressure so It doesnt really help if the pump works if regulator lets by all the fuel...

Since I dont have a gauge here now, I will fit an adjustable pressure regulator set to 43 PSI behind the supposedly broken stock one. At least engine will behave differently than now..

The meter flap is moving nicely. I will also check the other things anyway

Ill get back to you with the outcome of the FP test.

Mats
User avatar
Murray
Verde
Verde
Posts: 622
Joined: Sun Nov 28, 2004 11:16 am
Location: Lac Brome Quebec - Canada

Re: Std 1986 engine stalls

Post by Murray »

Mats
You state " At least engine will behave differently than now.. " that may be true if your problem is tied to a faulty fuel pressure regulator but if the issue is elsewhere, pump, filter,lines,electrical system,etc. then the problem will still be evident.It's equally easy to insert a cheap guage which will give you a broader view of what's happening.
1986-GTV6
1989-75 Twinspark very sadly sold-remarkable sedan !
2014 Audi Q5 3.0l TDI - torque MONSTER
mats andersen
Silver
Silver
Posts: 4
Joined: Sun Jul 26, 2015 2:24 pm

Re: Std 1986 engine stalls

Post by mats andersen »

Hi

Yes fitting the adjustable regulator behind the stock one made the car work again.

Not sure what the pressure ought to be but sat it 43PSI / bar , it might be too much.
Anyone now for sure the stock pressure?

Anyway the problem is located and now I need to track down a working regulator or can they be repaired perhpas??

thank everyone:-(

Mats
User avatar
Murray
Verde
Verde
Posts: 622
Joined: Sun Nov 28, 2004 11:16 am
Location: Lac Brome Quebec - Canada

Re: Std 1986 engine stalls

Post by Murray »

Mats
Factory fuel pressure is approx. 36 psi/2.5 bar.Don't believe regulator can be repaired - sealed unit- but should be readily available more or less generic Bosch L-Jet component.Good Luck.
1986-GTV6
1989-75 Twinspark very sadly sold-remarkable sedan !
2014 Audi Q5 3.0l TDI - torque MONSTER
mats andersen
Silver
Silver
Posts: 4
Joined: Sun Jul 26, 2015 2:24 pm

Re: Std 1986 engine stalls

Post by mats andersen »

OMG!

As it was instantly better and revving freely I took it for granted that problem was sourced and ran out of the garage. I went back later today and tested it some more with 36 PSI pressure instead of 43PSI... The warmer it got the worse it got. Eventually almost as bad as before. Hmmmmmm. I tried of course adjusting pressure up and down without aiding the problem.

So I will now work my way through the other suggestions proposed earlier in the thread.

Mats
MR2 Zig
Verde
Verde
Posts: 766
Joined: Tue Jun 13, 2006 9:47 pm
Location: Fresno, Ca.
Contact:

Re: Std 1986 engine stalls

Post by MR2 Zig »

When was the last time the injector seals were replaced? I'm thinking that if more fuel is fixing the problem you may have a vacuum leak. That can destroy your engine with detonation.

The seal kits (one for each cylinder) are less than $5.00 here and are pretty easy to fit. They are a standard Bosch L-jet part.

I hope that helps,
Scott
MR1 Zig (I made rate!)
Machinery Repairman USNR
Post Reply