77 campmobile 2.0 ltr FI problems

[buck]

My name is Brian and I have a FI problem. Purchased a 1977 Campmobile that had been sitting in a warehouse for 14 yrs. PO apparently cleaned and replaced various fuel delivery components and had bus running, but when I went to look at it bus would not idle or stay running. I had the "fever" so I bought it anyway. PO replaced fuel filter, fuel pump, 4 fuel injectors (not CS valve), fuel lines. Claimed he was using it as daily driver, but it recently started running poorly. I have replaced AFM, intake runner boots, intake manifold gaskets, throttle valve to air intake plemum gasket, points, condensor, vacum lines, fuel filter (had more rust from fuel tank), temp sensor II. Added fuel pressure gauge, set timing, points, checked valve adjustments (correct per bentley's). Adjusted AFM per colin's tech article. This is where I am now; Bus will crank and start to run but does not want to idle until warmed up slightly. Once warmed for a couple of minutes bus will idle and run somewhat correctly for about 15 minutes (typical driving), then gradually starts to sputter @ high RPM's and eventually won't go past 55 mph. I have adjusted AFM both static, dynamic, and mix but can not seem to get i t dialed in. A few notes: AFM static adjustment is adjusted so adjustement screw is all the way to left of slot (full adjustment of sweeper arm CCW). Dynamic adjust has been adjusted both loose and tight. It appears engine heat related. Any ideas?

Thanks

Buck

[vwlover77]

My guess would be fuel delivery issues due to junk in the fuel tank clogging the outlet line to the fuel pump. When it starts to lose power, gently stop so as not to cause a big slosh in the fuel tank and listen to the fuel pump. Is it whining loudly? Then it's starving for fuel.

This may also be why that wiper arm in the AFM has to be all the way to the CCW direction. This may be a gross compensation for lack of sufficient fuel.

Also, the fuel pressure gauge will fool you. The pressure may be OK, but the pump may not be able to deliver the volume needed.

This can be a gradual problem. When you first start the engine, the debris in the tank may have settled and moved away from the fuel line outlet. As the fuel pump begins running, the debris begins to collect at the outet line, drawn there by the flowing fuel. Eventually, enough junk builds up to restrict the flow. If it is big enough debris, it won't flow down into the filter where you can see it.

I would also recommend doing the fuel pump VOLUME test as described in the Bentley.

[Amskeptic]

My name is Brian and I have a FI problem.

HI BRIAN! (said with 12-step enthusiasm)

cleaned and replaced various fuel delivery components
I have replaced AFM, intake runner boots, intake manifold gaskets, throttle valve to air intake plemum gasket, points, condensor, vacuum lines, fuel filter (had more rust from fuel tank), temp sensor II. Added fuel pressure gauge, set timing, points, checked valve adjustments (correct per bentley's). Adjusted AFM per colin's tech article.
Bus will crank and start to run but does not want to idle until warm
bus will idle and run somewhat correctly for about 15 minutes then gradually starts to sputter @ high RPM's and eventually won't go past 55 mph.
AFM static adjustment is adjusted all the way to left of slot
Any ideas?

Idea #1. Thou Shalt Not Throw Parts At It

Idea #2 Vacuum leak somewhere. All of the adjustments you have listed here are compensatory, and have given you running when it shouldn't, but you have robbed Peter (operating temp parameters) to pay Paul (cold start).

Colin

[midatlanticys]

Hi Brian, welcome aboard! This might be unrelated to your FI problem, but I'm curious why you replaced the AFM? Was there an obvious problem with the original? or was it not original and/or the wrong one for your motor?

[buck]

Don - Thanks for the reply and tips about fuel pump. Fuel pump troubleshooting is next on the list. Fuel filter was replaced and old filter had a lot of rust particles in it. Is it possible for rust particles to make it past the filter and foul up the pump?

Colin - I see you picked up on the subtle reference to the 12 step program. I have become obsessed w/ fixing this bus. Being a newbie to VW's, foreign car resto, and unfortunatley not aware of this website, I am guilty of breaking rule #1. In regards to rule # 2, I have checked, repaired, replaced or temporary removed from FI circuit all vacuum lines, connections, etc. - not ruling out vacuum leak is problem, but feel fairly comfortable vacuum leaks have been found and corrected.

Midatlantic - AFM replacement - newbie mistake. Took bus to local VW dealer (figuring they would be the best candidate to fix - boy was I wrong). The VW dealer replaced the AFM, intake runner boots, and intake manifold gaskets, but still could not make it run right. I got fed up and went and got it and realized If the bus was ever going to run right and not cost me a small fortune, I was going to have to learn to fix it myself.

More of what I have done:

Read almost every post on this website that references FI or has subject line that is similar to the problems I am experiencing.

Vacuum leak stood out as most likely problem. Traced all vacuum lines, connections, etc. from thier origination to destination. Replaced or repaired all that were defective. Added hose clamps to all end connections. S-boot is in great shape, no cracks or splits. Temporary took brake booster out of FI circuit to make sure it was not the guilty component. Checked oil filler cap, dip stick, valve cover gaskets- all seem to be operating as designed.

Adjusted AFM according to Colin's tech article. maxxed out CCW static adjust is obviously red flag, but can't figure out what it is trying to tell me. Dynamic adjust has been from tight to loose spring w/ obvious changes in engine. Temp seems to affect how dynamic adjustment affects engine performance.

Replaced points & condensor, adjusted points, set timing (7.5 btdc @ idle, 38-40 btdc @ approx. 3000 rpm w/ vacuum advance on, 28 btdc w/ vacuum advance off). Note - drove bus for 4 hours in stop and go traffic and didn't experience problem ( thought I had fixed it. Next day decided to road test on open hwy. After approx 20 minutes problem started and progressively got worse.

PO installed new dbl relay. Checked w/ multi-meter to make sure of proper operation. (checked ground connection just above dbl relay).

Plugged EGR tube where it exits engine bay. EGR filter is gone.

Installed fuel rail pressure gauge. Maintains approx. 32 psi when idling, 28- 30 psi @ higher RPM. Pressure remains for approx 4- 6 hrs after shutdown.

Replaced temp sensor II - New temp sensor is approx 1800 ohms @ outside ambient temp of 75. Just out of curiosity I checked old temp sensor - it had a resistance of 4400 ohms @ same outside ambient temp.

The typ test session is like this:

Crank bus - initially hard to crank, turns over but doesn't immedietly fire up. takes about 5 seconds and 1 - 2 turn key off/turn key back on. Once running it doesn't want to idle unless you manually adjust AFM (static CCW). Once warmed up it will hold idle, but after about 15 - 20 minutes of driving starts to hesitate and lose power/speed @ high rpm/high gear/high speed. Progressively gets worse, hesitates and sputters through all gears speed ranges.

So - even though the symptons point to vacuum leak, could this possibly be electric problems? What am I missing? Going crazy, bus is consuming my life. Actually dreamed my wife was equipped w/ fuel injection sytem that was experiencing problems ( I know - weird!)

I am starting w/ fuel pump trouble shooting this weekend, and then will step back to vacuum leak trouble shooting again.

Please offer any diagnosis/ answers/suggestions.

Thanks

Brian

[chitwnvw]

Have you checked out the AAR? Auxilliary Air Regulator...I think. Meant to offer extra air to the engine while cold and then wean as it warms up.

I don't think rust can get downstream of the filter, but it can restrict fuel flow. Since you've said you have found rust you may be a candidate for a future fuel tank overhaul.

[Kubelwagen]

Not an expert.

However, I can give words of encouragement: it sounds like you're taking this on in a very methodical manner and you will get to the bottom of it. I'm a newbie here, but the collective knowledge around these parts is amazing.

[midatlanticys]

14yrs in a warehouse with anything less than a full gas tank could point to rust & crud. Any chance the VW garage still has the original AFM?

[buck]

OK, still don't have bus running correctly. Need help.
Latest fixes - removed fuel tank, cleaned and sealed per Ratwell's DIY fuel tank rehab. A lot of rust came out, (approx 2 cups of chips and dust). Tank inside completely rust free and sealed w/ POR-15. All outlet, inlet and vent lines checked for clogs. Replaced fuel filter. Had previously checked fuel pump for proper volume output (filled up 2 ltr bottle in about 45 seconds). Replaced coil and plug wires, reset points to specs, set timing to specs. Checked all vacuum lines/hoses, no leaks found. Reset AFM back to original factory settings (static @ midpoint of adjustment, dynamic @ what I beleive to be original setting, bypass @ 4.5 turns up from bottom out).
Test time - engine slow to crank and won't hold idle, adjust throttle valve bypass to increase idle, fiddle w/ sweeper by hand, engine @ idle tells me it wants more sweeper adjust CCW. I loosen dynamic spring to allow air flow to move sweeper CCW. Revved engine to approx. 3000 rpm and engine tells me it wants more static adjust CCW. I loosen dynamic (again)to allow for air flow to move sweeper CCW. Now sweeper won't shut off fuel pump when engine shut down. Even w/ adjustment to small arm, dynamic spring does not have enough force to move fuel pump shut off arm. So, adjusted static CCW and tightened dynamic to resolve problem(s).
Test Ride - engine runs OK in low rpms, starts to sputter @ high rpms thru all gears. Problem gets worse as test ride gets longer (heat related?) Returned to garage, checked timing, checked for vacuum leaks, gas leaks. Frustrated- gave up for the day.
Next day-Checked and adjusted intake and exhaust valves to spec. Replaced valve cover gaskets.
Test time - engine cranks right up, but won't run right. I fiddle w/ sweeper and engine tells me it wants sweeper adjust CW @ idle and 3000 RPM. I tighten dynamic to to adjust sweeper CW.
Test Ride - engine runs good, slight hesitation @ low RPM and high RPM thru all gears. Engine runs like this for about 20 minutes of back roads driving and then starts to progressively get worse. Bogging thru out rpm range thru all gears. I barely get home. Frustrated - call it day. Almost ready to sell bus. Anybody got any ideas or advice?

[vwlover77]

Making AFM adjustments on a cold engine is not a good idea. Get it good and warm, make the adjustments, and then deal with the cold issues.

What is the condition of the FI wiring harness?

Are the grounds on the driver's side of the air plenum clean and secure?

What is the condition of the resistor pack up by the double relay? Check all connections inside its plug to make sure they are clean and tight.

Finally, what is the condition of the main wiring harness plug at the ECU? Check for bent, corroded, or sprung-open connections on the harness plug and check for clean and secure pins on the ECU itself.

You've already replaced everything in the ignition system (coil, wires, cap, rotor, points, condensor, plugs), right?

You said all vacuum lines replaced. Does that include that 90 degree rubber elbow on the Aux Air Regulator? It's buried and is a common failure point.

[Amskeptic]

Need help.

Help and a scolding. Nags will be in red.

Reset AFM back to original factory settings (static @ midpoint of adjustment, dynamic @ what I beleive to be original setting, bypass @ 4.5 turns up from bottom out).

This is not a part that you can just "reset" to what you might guess were "the original factory setting". Static at midpoint could be devastatingly lean. The dynamic could be guessed right to the Blowtorch The Exhaust Valves lean.
We are only allowed to touch that AFM with the engine running at operating temperature. You screw with that thing without the engine telling you what to do, you are sliding straight to terminal confusion.

Test time - engine slow to crank and won't hold idle, adjust throttle valve bypass to increase idle, fiddle w/ sweeper by hand, engine @ idle tells me it wants more sweeper adjust CCW. I loosen dynamic spring to allow air flow to move sweeper CCW.

Please read the AFM Adjustment article. Engine at idle did not "tell you" it wanted more "sweeper adjustment" and the spring is not the "sweeper adjuster". This stuff can be critically dangerous to the health of your engine if you do not grasp the concepts.

The engine tells you "I want more fuel" or "I want less fuel". Period.
It tells you at idle, and it tells you at high rpm, because you ask it at idle and high rpm.

You are the guy who decides which and in what combination of the three adjustment procedures you use. The general rule, and I am not going to write the whole damn thing out here again, is that the wiper adjustment is only changed IF the engine has told you that it wants the same more or less fuel BOTH at idle and high rpm. The dynamic adjustment is only changed if there is a difference in desire between idle and high rpm.

Revved engine to approx. 3000 rpm and engine tells me it wants more static adjust CCW. I loosen dynamic (again)to allow for air flow to move sweeper CCW. Now sweeper won't shut off fuel pump when engine shut down. Even w/ adjustment to small arm, dynamic spring does not have enough force to move fuel pump shut off arm. So, adjusted static CCW and tightened dynamic to resolve problem(s)

You are deeply lost here. As written in the AFM Adjustment article, you *bend* the little silver arm that touches the fuel pump contacts to shut the pump off when the engine stops. You do not change the mixture to shut off the fuel pump

engine runs OK in low rpms, starts to sputter @ high rpms thru all gears. Problem gets worse as test ride gets longer

Rich is my guess.

I fiddle w/ sweeper and engine tells me it wants sweeper adjust CW @ idle and 3000 RPM. I tighten dynamic to to adjust sweeper CW.

So you leaned it out, but used the wrong method.

Almost ready to sell bus. Anybody got any ideas or advice?

Read the AFM Adjustment article (sticky in the Fuel Delivery forum) and write back here if it makes sense . . . before you terminally lose yourself in the labyrinthe of adjustability afforded you inside the AFM. You need to know what you are doing before you can adjust the AFM. Where are you located?
Colin

[buck]

Don,

Thanks for the reply.
AFM adjustments - initial adjustment made to make engine run w/o bogging down/cutting off, basically to hold idle. Typical test session includes let engine run @ idle for approx. 5 min, then adjustments made to AFM in accordance w/ Colin's tech article; move sweeper arm ever so slightly each way @ idle and 3000 rpm, listen to engine response, make adjustments to static and/or dynamic to achieve correct engine performance.

FI wiring harness appears to be in better than average shape, no nicks, cuts in cable sheath, all connections ends not corroded or oxidized.

Grounds on driver's side air plenum - have not checked but will and verify

Resistor pack appears to be original - will clean and verify all connections
Dbl Relay replaced by PO right before I purchased vehicle in attempt to correct poor running problem.

Checked ECU connections pins and harness ECU connection, all seem to be in good shape, no bent pins, corroded sockets, etc.

Have not replaced cap or rotor as both appear to be in good shape.

Replaced AAR 90 boot and hose

Thanks for the tips and constructive help.

Colin,

Thanks for the reply. Scolding and nags duly noted.


Brian
Freeport, Florida

[Gypsie]

Also remember to check the impact any changes in the settings make before moving on to another adjustment.

any change made inside the afm box will impact the other settings and may require corresponding corrections.

As I have become intimate with my afm I have gained a more ready understanding of adjustments and impact. It took some time though to begin to put it all together. Take your time to fully grok the interplay so that you are making considered adjustments and not making frustration for yourself.

Since you are digging deep, take an ohm meter to the afm connections and confirm that all is to spec. You can touch probes to the arms inside the unit instead of the blades for ease, just make sure you are spec'ing to the right connections.

If you have the ohm meter handy you might as well check some of the other checkable items like the series resistor block and coil, though I am leaning to fuel mix issues.

You can do some other 'ez' testing by pulling one plug wire at a time (fully warm at idle) and noting what impact it has on the engine. Typically each should have an equal impact. One wire removed with no impact can point to a fault in that cylinder. The fault could be electrical, fuel, compression...???.

Have you tested compression?

What do your plugs look like after these short tests?

You're almost there, I can feel it.

[Amskeptic]

Typical test session includes let engine run @ idle for approx. 5 min, then adjustments made to AFM

That is insufficient to warm up the engine properly. I will drive my ass down to Florida and you WILL give me a cup of coffee if you do not have a beautifully running bus and the easy familiarity with the AFM that all of us here at the IAC demand of you by let's say, October.
Colin

[midatlanticys]

Brian, didja ever get this bus straightened out? If not, the following is a trump card

. . . I will drive my ass down to Florida and you WILL give me a cup of coffee if you do not have a beautifully running bus . . . . by let's say, October.
Colin