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Discussion Starter #1
I can't figure out my car. I'm leaning toward some sort of fuel delivery issue, possibly gunk in the tank. I don't have a fuel pressure gauge but Harbor Freight has theirs on sale for $20, so probably a sound investment. I tried Greg Gordon's technique of using a cylinder compression gauge, but that ended... poorly. FYI, the car sat with minimal fuel, stabilized with Seafoam, for many months. When I purged the tank it was black. No solid material though.

ANYWAY, the car runs so roughly (cold and warmed up) that I'm worried something is going to explode, break, or otherwise cease to operate. The last time I drove it any measurable distance, about 3 weeks ago, it died when I lifted the throttle. No sputtering, no complaining, it just shut off, then wouldn't restart for many minutes.

I've checked every vacuum line, the AFM snorkus, the plenum connectors (a couple were in fact loose), installed a new air filter, cleaned and regapped the plugs, adjusted the timing, changed the oil, tested the plug wires, cleaned grounds (basically Greg's entire L-Jet walkthrough) and even did a dance to the snake god.

I have NOT yet drained the fuel and pulled the screen, or cut open the old fuel filter to check for crud. The reason is dumb - I don't have a suitably sized container to put the fuel into. I'm guessing there's about 3-4 gallons in the tank. I also can't seem to hack through the filter casing. I clamped it and sawed until my arm fell off, and barely nicked it. Must be made of adamantium.

At this point, barring some diagnosis with the fuel pressure gauge, I'm left with taking it to the mechanic, unless anyone has some mystical or clairvoyant insight. Maybe I can get some video/audio of the thing this evening.
 

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Discussion Starter #3
Timing belt is still on the dots, but I still have the cover off so I'll check again.
Compression is good. The #6 cylinder is a smidge low but within acceptable range.
I ohm tested the wires (original style, with capacitors), and also pulled the plugs to visually confirm they were firing, even while wiggling the wires to check for shorts. Also used an inductive tester at multiple points on each wire.
The coil wire had been loose and I suspected that was the problem, but I'm getting consistent juice to the distributor.
Maybe it's a cruddy rotor or cap? They're new-ish and recently cleaned, but also AutoZone generic.
Maybe the fuel tests will shed some light. The regulator is new, the filter is new, the injectors recently cleaned and recapped by Greg's shop, but the pump is original, as are the hoses and lines. As far as I know the tank has never been removed, cleaned and relined. I'm dreading that possibility, as I've read about the (expensive) headaches caused by the intricate baffling.
 

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I had the key break off the inside of a rotor recently. Caused VERY poor running.



Also, can you check the fuel flow in the carbs while someone cranks the motor?
 

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Discussion Starter #5
I could if it hard carbs! Bosch L-Jet in '82.

You know, I checked the cap and the rotor, but I didn't really inspect it super closely. I'll pull that apart again, too.
 

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Probably worthwhile to pick up that HF fuel pressure gauge, I use one and it works well. As you suspect it could be a clogged fuel filter, the pressure gauge can help determine that.

Does it always run poorly now? Had you removed the wires for any reason prior to that happening and maybe put them back on in the wrong order?

Kevin
 

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Discussion Starter #7
The fuel pressure gauge was on sale for $20, so I nabbed one even though is specifically said it wasn't for Bosch systems. As with most diagnostic tools in the stash, it'll be modified. I guess the t-junction can go in-line with the cold start injector?

I didn't start messing with the plug wires until the symptoms first started up. The problem wasn't predicated by any tinkering though. It started running poorly in the fall so I pulled off the plenum and reseated it, as a couple of the connectors were fidgety. I also replaced the air filter and did some vacuum hose maintenance, replacing a couple that were looking brittle with silicone and installing a couple of new clamps where needed. The problem seems to be getting increasingly worse, with the sudden stalling out being the latest issue.

So I'm leaning toward a fuel issue, but I really won't know until I drain the tank. I did find a local shop that would clean the tank for under $200, but I'd probably still need to replace the fuel hoses and clean the hard lines too, if the tank is indeed sludged.

I read on the old BB that some guys had removed the mesh in the banjo fitting and installed a high-flow filter between the tank and the pump, which basically eliminates the possibility of any gunk getting into and fouling the pump. I just worry that the old pump in the car might not be able to draw adequate fuel through a filter. Thoughts? I think Greg Gordon was a proponent of this setup.
 

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Check the AFM and the throttle position sensor connections thoroughly.
I had corrosion up inside the plug on the wiring harness and my TPS was acting dodgy.
I have a TS Motronic, not L-jet.
I clipped the connector off and hard wired it and that seemed to resolve the issues.
 

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The fuel pressure gauge was on sale for $20, so I nabbed one even though is specifically said it wasn't for Bosch systems. As with most diagnostic tools in the stash, it'll be modified. I guess the t-junction can go in-line with the cold start injector?
That's exactly what I do on my Milano.

Kevin
 

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Seal the pipe threads on the HF fuel pressure gauge with teflon tape before use.

Ask me how I know to do this!
 

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Kaga mate, it will end up being one of those Alfa moments which you'll laugh about for years!
The sudden stall? That sounds like a sensor/gadget failure to me rather than fuel. How does the L-jet pick up the timing?
Later motronic Alfas have a crank sensor which fail as you described which in the lead up start to die when they/engine warms up.
Is there an intank fuel pump? Has the fuel line come loose off it?
Is the fuel dirty or clean pre or post filter? May have a clogged filter, I normally use tins snips on filter canisters, I've also seen the manual style campIng can openers used. The type that has a short plunger and then you whittle it around the can. Can you drain the fuel into another vehicle, although you may just be transferring bad fuel, hmmm. Maybe get a bunch of large water containers, toss the water out and collect your fuel. Plastic fuel jerry cans aren't too offensive in cost and it's handy to have a can of petrol as a solvent anyways.
How are the basics, do we have fuel, spark, compression? Sounds like you've touched on some of these.
Poor idle is an AFM/MAF issue normally or vaccine leak, which again you've looked at.
Anyhow, I guess what I'm getting at is to be sure that the L-jet sensors are ok and that the engine is receiving its basics. Certainly frustrating to have stowed her in working order, to this. She's probably just pissed at you for abandoning her!
 

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Discussion Starter #12
Well, the week has been so busy that I haven't even had a chance to pop the hood. Hopefully the weekend will allow a few hours, although I also have to continue my garage organization project and also insulate the garage door. Picking up a 5-gallon galvanized metal can for the fuel though. Even if the fuel pressure is OK I want to visually inspect the interior of the tank.

Maybe the ignition coil is bad, and is just randomly dropping spark? How would I test that, short of just replacing it? I don't think the GTV6 has any sort of a crank sensor. Possibly a faulty TPS, or maybe wiring to the CTS or TTS, per Greg Gordon's writeup?
 

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No crank/flywheel sensors in the GTV6.

Since L-jet is so sensitive to 'false air', I wonder if you could try something like what I did to find some well-hidden air leaks in our Spider. See: Embarrassing Confession.

I did not have any luck with 'smoke' tests (waving a smoke generator around the engine looking for the smoke to be blown away or sucked in) or spraying a combustible near suspect areas. What I did was use ~ 10psi of air pressure to fill the engine/air ducts (by blocking the AFM with a piece of 'freezer wrap' - heavy duty plastic sheet) and sticking an air hose at 10 psi into the dipstick tube. I then listened with a 2' length of heater hose as a stethescope &/or sprayed soapy water at suspect areas. Even though the leaks I found seemed rather small, they did mess up the operation of the engine.
 

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From the description you give, I'll bet a six pack of somebody's favorite brew you have fuel feed problems. Start at the source and work forward, including blowing out the hard lines and replacing all the rubber hose sections. You got to be certain the fuel pump and filter are 100% in working order. And don't rule out the fuel pressure regulator up front.

On another note, are you sure the engine ground strap and other grounds are clean and tight? Looked into your air flow meter lately?
 

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Discussion Starter #16
I replaced the fuel pressure regulator about 3 years ago with a brand new part. I was getting solid numbers for pressure at the cold start injector, which would indicate there's no permanent blockages in the lines or filter. However, I haven't ruled out loose crud in the tank that is intermittently clogging the outlet. Also haven't ruled out the pump losing juice intermittently. I plan to pull the pump and do some bench testing.

Maybe it is an air leak problem. If the car is running as poorly as it is on startup with good fuel pressure, that makes the most sense. I'll pull all of the vacuum lines and air hoses again. Maybe I'll just replace the remainder of the old ones with silicone. Why not?

I suppose one of the plenum connectors could still be a problem. I still need to do the compressed air test ghnl recommended. Unfortunately this past weekend wasn't the time to get anything done. I had maybe half an hour to dedicate to the car. So it goes!
 

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I don't remember if you've mentioned earlier in the thread, have you swapped in a known-good fuel relay? They can behave in strange ways when they go bad.
 

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Hey, my comment here is very unscientific, and born of experience. I had horrible rough running problems on my 76 Alfetta Sedan for a week after I added Seafoam. I will NEVER use it again. I had to burn through a tank of premium before the problems went away. Haven't had a problem since then. I hate to knock a product, but I am convinced that stuff is not good for our engines.
 

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Discussion Starter #20
Did you just run it through the tank, or did you do the entire "procedure" of sucking it through the plenum? I've had good luck just using it as an additive.
 
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