Are my plug wires bad and if so would that cause stalling after the car is hot? - Page 10 - Alfa Romeo Bulletin Board & Forums
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post #136 of 302 (permalink) Old 04-11-2017, 07:34 AM Thread Starter
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I haven't actually fired it up yet. Potential fuel leaks scare me so I want to make absolutely sure I'm not dumping gas before I give it spark.


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post #137 of 302 (permalink) Old 04-11-2017, 08:02 AM Thread Starter
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And yeah, if you go back to the video I posted on Page 7, the fuel pressure gauge is steady. Now it's swinging wildly, and several PSI higher.

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post #138 of 302 (permalink) Old 04-12-2017, 07:37 AM Thread Starter
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Well, now I'm not sure what's going on. When I got home from work yesterday I pressurized the system and pinched off return line after the FPR. A couple of hours later, it was still at ~35psi. Probably not the pump's check valve, then. Good - it's a brand new, out of the box pump! So I unclamped that hose, repressurized, then clamped the send line. A couple of hours it was holding steady at ~35 psi.

Weird. Still not ready to give it spark though, being worried about a potential fuel leak. By then it was late so I unpinched the hose and went to bed. This morning, with no clamped fuel hoses, pressure was still at ~35 psi.

Huh.

I'd chalk this up to a faulty gauge, but the pressure loss was recorded by two different gauges. There was a seeping leak at the gauge during the first run of tests but I've since resolved that, with pressure loss still recorded afterward. Other than tightening that connection, clamping the pressurized hoses, and putting a vacuum hand pump on the FPR, nothing has been done to the components. I haven't fired the engine, so I doubt if an injector was stuck that it would become unstuck, if that's even possible. Haven't swapped any other components, not even a hose clamp.

Any theories as to what's going on? MAYBE the FPR diaphragm or spring is bad but not broken, and making it work by increasing the fuel pressure (overpressurizing by deadheading the return line) or applying more vacuum, via the hand pump, than it would normally experience kinds sorta fixed it? That might explain the intermittent periods the car would actually run decently well. And is it possible that a bad FPR diaphragm could cause a significant vacuum leak, enough to drop my gauge to the levels it was displaying? I doubt it, but I really don't know.

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post #139 of 302 (permalink) Old 04-12-2017, 08:06 AM
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If you want to rule out the FPR diaphragm, why not disconnect the two hoses and apply vacuum (normal engine range, 19 to 21" hg max) to the signal port? If it holds vacuum, then it's not damaged. And then you know you're NOT sucking raw fuel into the plenum, right?

There's really only 3 parts, the spring, the diaphragm and the seat.

But-- if it's holding 35 psi pressure, with no clamp on the return line like you said, then that says something good about both your injectors and the fuel pressure regulator. The pump is therefore holding pressure within the system.

At this point, I'd fire it up, and observe both the vacuum reading and fuel line pressure, Mr Chairman.

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post #140 of 302 (permalink) Old 04-12-2017, 08:12 AM Thread Starter
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I am planning to replace the fuel pressure gauge fitting with one that is metal and fits the hose diameter better, along with the new, small gauge. That should arrive from Summit tomorrow. Once that's in and I confirm there no leakage, I guess I should just give it some spark and see what happens!

I still find it weird that I can see a sudden and complete loss of fuel pressure in the morning then a <5% loss later that day! The fact I've seen intermittently normal running, but mostly problematic, makes me want to fully resolve the problem, whatever it is.
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post #141 of 302 (permalink) Old 04-12-2017, 08:19 AM
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I understand... it comes and goes. But you're slaying the dragons, one at a time. I'll bet you have improved vacuum, at least, if the FPR is ok.

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post #142 of 302 (permalink) Old 04-13-2017, 11:23 AM Thread Starter
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Sigh. I wonder if this engine doesn't just want to die.
Dive into it again last night, looking for the leak. Checking the timing belt and cam timing. Ignition timing. Injectors. Fuel supply. Vacuum hoses. Everything in the L Jet tuneup guide. Didn't find much aside from a slightly loose plenum hose clamp. Fired it up and after a few seconds not only did it still suffer catastrophically low vacuum and began stalling, after about 30 seconds it began pouring out acrid white smoke from somewhere in the engine bay. I couldn't tell exactly where as I shut the thing down as fast as I could. I gave it a few minutes to make sure it wasn't actually on fire.
At this point I assume something is truly, badly wrong with it.


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post #143 of 302 (permalink) Old 04-13-2017, 11:53 AM
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Good Lord! Did it have that ozone smell, like a dead electrical short?

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post #144 of 302 (permalink) Old 04-13-2017, 11:59 AM Thread Starter
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Not really. No. This was more of an oily smell.
There's no evidence of a blown head gasket - no milkshake, no external leaks, no mess in the cylinders. But it does seem like it's in the head(s).
Looks like I'll be methodically tearing down at least the fuel and ignition system if not more. Whee.

Thoughts - the engine didn't seem to be running long enough to generate the heat to burn anything externally, like spilled oil on the exhaust or anything like that. From experience that'll take a minute or two at least! So the smoke must've come from inside the engine. So how was it getting out? It definitely wasn't from the throttle body or AFM. It seemed to be more under the plenum.

I also dipped the new injector seals in oil prior to installing them, although I can't imagine there was enough oil on them to generate that amount of smoke. But maybe?

Wondering if one of the intake tubes isn't the leak culprit, and the smoke WAS the oil on the injector seals?

All speculation at this point.
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post #145 of 302 (permalink) Old 04-13-2017, 01:07 PM
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If you spilled/leaked any oil on the exhaust manifolds, that'll make quite a cloud as soon as they heat up.
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post #146 of 302 (permalink) Old 04-13-2017, 01:08 PM Thread Starter
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No, there was no spillage of any oil/fluids on the manifolds. This very much seemed to be coming from the plenum area.

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post #147 of 302 (permalink) Old 04-13-2017, 01:11 PM
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Sounds like the fuel/air charge being blown back out somehow. No backfiring or popping?

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post #148 of 302 (permalink) Old 04-13-2017, 01:14 PM Thread Starter
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No, no backfiring or popping. Vacuum is still extremely low - 10-12" - and as before even breathing on the throttle causes an immediate stall. It did run long enough to confirm the distributor retard works and timing is OK, although a bit advanced (more on the P/F line rather than the R, although this is probably because it hadn't run long enough for the idle to drop).

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post #149 of 302 (permalink) Old 04-13-2017, 06:29 PM
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Looks like you need someone to start the engine while you watch the engine bay closely so you can see where the smoke/vapor is coming from. Then go from there.
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post #150 of 302 (permalink) Old 04-15-2017, 08:00 AM Thread Starter
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Yeah, seems there was some residual lubricant on the injector seals that was smoking. However, I've still found no obvious culprits. None of the seals were pinched. The injectors do not leak. The timing marks on the cams are still perfectly aligned and belt tension is fine. None of the hoses have hidden tears. I was going to put some air into the plenum and listen for the whistle but I accidentally knocked over my compressor and broke the outlet valve. Then I dropped my torque wrench and broke that, too. Thankfully that's a Craftsman and Sears confirmed via phone they will replace it for free.

It's holding fuel pressure, at least.

So I'm still at a loss regarding the vacuum. It's still stalling instantly if I even breathe on the throttle. You can watch the vacuum go from a measly 12-15" to 0 when I do.

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