Are my plug wires bad and if so would that cause stalling after the car is hot? - Page 5 - Alfa Romeo Bulletin Board & Forums
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post #61 of 302 (permalink) Old 03-23-2017, 07:25 AM
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Hi

You said

"Except it doesn't always have to be hot - sometimes it runs poorly within seconds of starting. Sometimes it's fine. A few weeks ago I ran it for several hours with no issues. This past Saturday it started stalling in less than 5 minutes. Stalled out. Parked for about 2 hours, refused to start the first three tries waiting about 15-20 seconds between cranks, but the fourth it fired right up and had no more problems. I even drove around the neighborhood for about 15 minutes to see if it would stall out, and it ran like a top."

This does not sound to me like a fuel problem of any kind. It very much sounds like a wiring issue. Now I'm not next to the car and can't hear it, but to me there is a wire with an intermittent break or an intermittent ground, something like that or an ECU problem.

What year GTV6 is this ?

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post #62 of 302 (permalink) Old 03-23-2017, 09:42 AM Thread Starter
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An '82.

MAYBE it's the AFM or ECU? I don't have a spare of either, though. As I said, I've replaced wiring, sensors, grounds, and everything is clean, tight, and coated with dielectric grease (where appropriate).

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post #63 of 302 (permalink) Old 03-23-2017, 09:59 AM
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I wanted to question the ECU, Mr Chairman, but somehow I had the idea you had already tested by substitution. Surely somebody can loan you another ECU to plug in and test. I think you're getting close to a solution. Lord knows, you've been through everything else.

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post #64 of 302 (permalink) Old 03-23-2017, 10:03 AM Thread Starter
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No, I've never been able to test the ECU. We had it out and inspected it for dry joints, corrosion, or obvious issues, but it SEEMED fine. Cleaned and lubed the harness and reinstalled it. But I'll put out a call for a loaner spare, if anyone is willing.

I now have a checklist, most of which is rechecking things I've already gone through. Fuel pump, AFM, ECU, sensors, grounds. I think I might go ahead and install a permanent fuel pressure gauge on the CSI hose, too. It's something I've been meaning to do for ages but just haven't, for whatever reason. I know I've seen some examples of that here. Seems useful.

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post #65 of 302 (permalink) Old 03-23-2017, 10:11 AM
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Checking out that ECU by substitution with a known good one will be quick and easy. But don't do that in conjunction with anything else... one variable at a time, right?

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post #66 of 302 (permalink) Old 03-23-2017, 10:15 AM Thread Starter
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No, no. One thing at a time. Until I can get my hands on one though, I'll start with the easy stuff. Also replace 5-8 (again) and clean/test the connections in the fusebox. Check the intertia switch bypass. Fuel pump electrical continuity. Grounds.

Or maybe I have a "floater" of sludge in the gas tank that was obscured by the baffles last time I scoped it. Always a possibility.

It's the random and intermittent nature of the problem that makes this one tricky. I've thought I've fixed it several times, only to have it re-emerge. Also made harder because I had OTHER issues causing the engine to die, like a bad coolant temp sensor and dying coil, that resulted in non-running situations.

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post #67 of 302 (permalink) Old 03-23-2017, 10:50 AM
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I had an identical problem with my 105. Of course, I had fewer bugs to chase as it's a far simpler car than your GTV6. The problem was poorly made spark plugs leads, and I resorted to making my own to ensure proper connectivity.

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post #68 of 302 (permalink) Old 03-25-2017, 12:43 PM Thread Starter
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Huh. So I've been crawling around under the car today and noticed something. The lead from the oxygen sensor was gone. As in, ripped out of the sensor, leaving only a little nub of wire. Now, I was under the impression that you could run without an O2 sensor, it would just run rich. But given my car seems to start experiencing its issues when the engine warms up... I'm gonna fix it now. More to come.

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post #69 of 302 (permalink) Old 03-25-2017, 01:01 PM
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post #70 of 302 (permalink) Old 03-25-2017, 01:31 PM Thread Starter
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Nope. No difference.
This is still what's happening, after hooking the sensor back in.
This has to be a fuel starvation issue, right?
I'm draining the gas tank now, and will scope it after I get back from the pool with the kids. Check the hardlines, send and return banjos, in-tank screen, etc.
Priorities!

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post #71 of 302 (permalink) Old 03-25-2017, 03:46 PM
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No it doesn't have to be fuel starvation.

Quote:
Originally Posted by chairmankaga View Post
Nope. No difference.
This is still what's happening, after hooking the sensor back in.
https://www.youtube.com/watch?v=TpE3aXee4Vc
This has to be a fuel starvation issue, right?
I'm draining the gas tank now, and will scope it after I get back from the pool with the kids. Check the hardlines, send and return banjos, in-tank screen, etc.
Priorities!

No. Based on that video, I would not say it has to be fuel starvation. Certainly not fuel starvation, in the usual sense of the word, meaning a weak pump or bad regulator or a blockage in a fuel line i.e. anything that would cause there to be insufficient fuel pressure in the injection rail.

It could be fuel starvation but I'm inclined to doubt it.

That video would have been much more useful if there had being a fuel pressure gauge hooked in line with the hose to the cold start injector(CIS). If you could see the fuel pressure decline as the engine stalled that would pretty much give you your answer.

So go get get yourself some 5/16 high pressure fuel line, and a selection of adaptors and plumb a fuel pressure gauge into the line that feeds the CIS. Watch the gauge as the car is turned on and after the car is turned off to get a feel for what good numbers should be.

Hope this helps

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post #72 of 302 (permalink) Old 03-25-2017, 04:45 PM
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Fuel gauge plugged in continously

Found the image of a gauge plumbed in semi-permanently. This comes from another AlfaBB user.
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post #73 of 302 (permalink) Old 03-27-2017, 07:37 AM Thread Starter
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So I finally got a decent fuel pressure gauge installed with no leaks and was able to monitor until it stalled and died. This is after I went ahead and pulled out the tank, which I've been meaning to do for years anyway. No rust, varnish or sludge, although the return banjo had some gunk lodged in the outlet. Checked all of the fittings, hoses, relief valve, etc. Purged the hard lines with carb cleaner and a few blasts of dry shop air. Tested current to the fuel pump, which was right at 12.8 volts continuously. All good.

After a couple of hard starts to get the gas flowing back into the engine, the car idled fine for a while with fuel pressure right at ~35psi. Then it started to drop rather quickly, maybe over about 30 seconds, to around 20 psi, whereupon it stalled and died. So I started it again, and the pressure would only increase if I pulled the throttle, before dropping again. I tried pinching off the return hose from the regulator with a pair of vice grips, with no noticeable change. Stall.

The fuel pump is new, after the original one seized after a prolonged stay in the garage. But what else could it be? I swapped three different combo-relays with no difference. Spark is strong. Battery is new. Current to the pump is full strength and consistent. Fuel filter is new but I'm going to swap one from the parts shelf, just to see what happens. Maybe it's waterlogged.

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'82 GTV6

Last edited by chairmankaga; 03-27-2017 at 08:22 AM.
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post #74 of 302 (permalink) Old 03-27-2017, 08:23 AM
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Your description is very good, and it first led me to think of the various things that could affect the pressure reading, either on the suction or outlet side of the pump. Mainly, the hoses themselves (the ID), or the filter maybe partly collapsed (which cannot be seen of course), but then I read your next paragraph:

"So I started it again, and the pressure would only increase if I pulled the throttle, before dropping again. I tried pinching off the return hose from the regulator with a pair of vice grips, with no noticeable change. Stall."

I could be wrong, but I think this is classic pressure regulator malfunction, either from a leaking diaphragm, broken spring, or some other internal problem. Because if you give it throttle like you did, it will demand more fuel, which will drop the pressure on the regulator outlet momentarily. It should catch up quickly though, if it's ok. Pinching off the return hose may not have any effect in this case... depends on how the regulator is failing.

So what's the story on the pressure regulator? Is there reason to suspect it in your opinion? You could have a bad pump... we've seen defective new parts before, but it's not my primary suspect at this point.

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post #75 of 302 (permalink) Old 03-27-2017, 08:33 AM Thread Starter
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The regulator was replaced maybe 6 or 7 years ago, after we determined the original was leaking. It would lose pressure QUICKLY after the car was shut down. Gas in the vacuum line too. Weirdly it ran OK-ish. The replacement was from eBay and significantly cheaper than retail, but it's Bosch and it was new in the box. Someone clearing out their parts surplus, I guess. I'm maybe a little suspicious of the provenance of any "new" car part from eBay, if I'm honest.

As I said, I'll go ahead and swap filters, since I have a new spare on the shelf. I always get several from RockAuto, since their shipping is so expensive. If that doesn't help, then on to the regulator.

FYI, all of my vacuum lines are brand new silicone hoses from Greg Gordon. No suspected leaks.

Is there a bench test for the part?

as good as a car can be... briefly.
'82 GTV6

Last edited by chairmankaga; 03-27-2017 at 08:36 AM.
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