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Discussion Starter #1
Hello,

I've searched/read every thread I can find related to this topic but would appreciate any feedback.

I'm experiencing a misfire which appears to increase in severity as the engine warms up. No electrical issues seen/warning lights. On start up and first 15mins of driving there are no issues. Misfire kicks in after approx. 15mins, and noticeably worsens after driving up an incline or when fuel tank volume lessens.

Actions taken:
1) Replaced spark plugs with NGK B7ES set at 0.03" per the set I took out. After reading further I'm going to adjust to 0.25"
2) Replaced ignition wires with new set from John Norman
3) Replaced distributor cap and rotor arm.

Next planned action - replace rear fuel filter in line with the fuel pump in case debris is in the line. PO did clean out of the gas tank but don't think it was relined. If this was an issue though, why would the car run fine when it is first ran?

If that doesn't help considering
1) The approach of Michael Keith as it does have the Fireball Ignition.
http://www.alfabb.com/bb/forums/gt-1963-1977/47634-latest-diagnostic-challenge.html#post416576

2) Looking at the Barometric Compensator as discussed by John Stewart in the SPICA FI Pump sticky.

3) Wondering about a new battery on the principle that it is probably a good thing to get checked.

Would appreciate all thoughts and guidance. New owner and very keen to learn how to maintain and appreciate the mechanicals of the car myself.

Thanks
David.
 

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Richard Jemison
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issues

You seem to think that your issue is ignition related, but symptoms are all fuel related per your discriptions.

Pull the fuel tank`s guage sender/fuel pickup out and check condition of attached filter and ANY rubber lines on the pickup or going to the pump..
They were not designed for alcohol fuels. Replace them all is the best solution.

Measure pump pressure at the spica pump. You should have a Spica manual if you are going to retain this induction system.
 

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You seem to think that your issue is ignition related, but symptoms are all fuel related per your discriptions.
Yup

MONSFDMM said:
3) Wondering about a new battery on the principle that it is probably a good thing to get checked.
I don't know what is causing your problem, but am 99.99% sure it isn't the battery.
 

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71 Berlina 74 GTV 17 Giulia Q4
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Does your low fuel pressure light work? Feel the pump when you first start it and again when it starts missing. If it's hot could be the pump is dying or a clogged filter.
What did the plugs look like? All the same or one different? If so what did it look like? Have you done a compression check? Could have good compression when cold and lose it when it warms up. Un hook the plug wires but leave them on and using a pair of well insulated pliers take one wire at a time off to see which one has no effect on rpm's.
 

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Maybe it's your coil? I once had an old 1975 Kawasaki 900 with dual coils. One coil sparked cylinders 1and 3, and the other coil sparked 2 and 4. After about 15 minutes of racing around town avoiding cops:punk: the bike started missing badly but would still run enough to get home.

The next day it seemed the problem had fixed itself so off I went until about 15 minutes into the ride when the same symptoms happened again. I nursed the bike back home again but when I pulled the plugs I found that plugs 1 and 3 weren't firing. It seems that when the coil warmed up, the thing crapped out. When it cooled off, it would fire the plugs again for a while. A second hand coil from the bike wrecker fixed the problem.

Maybe this is your problem--a faulty coil.

Good luck!
 

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It is hard to see how this is an electrical problem. Electrical systems do not normally work well for a certain time then act up. I am with Richard - check your fuel delivery system.
 

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71 Berlina 74 GTV 17 Giulia Q4
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Hard but not impossible. I to have had a coil break down and deliver a weak spark when hot and it feels exactly like it's running out of gas. Have a plan and stick to it. That's the best way forward.
 

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Discussion Starter #8
Thanks very much for all your replies.
Opened up the fuel tank and appears to be original fuel sender. Taken out and mechanism appears to be working ok.

Drained the fuel tank can see debris in the drained fuel. Took out the rear fuel filter and can see a lot of debris within that (after splitting it open).

Added new rear fuel filter and can see remaining debris within the tank using a small torch. Best way of removing crap from the bottom of a tank?
 

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Added new rear fuel filter and can see remaining debris within the tank using a small torch. Best way of removing crap from the bottom of a tank?
I had a similar problem with the fuel tank in my GTV6 but the debris in mine was destroying fuel pumps. I installed an industrial strainer immediately downstream of the tank discharge and I was able to periodically dump out the captured scale etc. I eventually bought a good fuel tank and swapped it out and the strainer kept me out of trouble in the meantime.
 

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David, before you do anything, tell me if you have a Marelli Distributor or some kind of electronic aftermarket ignition system? I'm in the repair and restoration business and have been collecting Alfas for 40 years. I have replaced many electronic ignition systems due to failures, and end up retro-fitting point and condenser systems and no failures.

When a car comes with a running problem, a compression test, leak down if necessary, cam timing inspection are performed first. Ignition system system is next and carburetion or fuel injection is the absolute last item inspected. If you have reasonably sure the engine mechanicals are up to snuff, go the ignition system. What you are describing sounds like a weak condenser. Once an older or even sometimes new condenser looses it's ability to "hold and disperse" voltage it can cause a poor running condition. As condensers get old they will short out when they hot and cause poor operation of the ignition system. If you have a point type distributor, replace the points and condenser, inspect the timing and test drive the car. I can't guarantee this is going to fix all your ills, but' its where I would start.

Sorry for the diatribe.
 

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As they are a cheap fix and easy to check, I'd go with the coil, before anything else on the fuel system.

Your symptoms are just as daveydog and gigem said for a failing coil, it's happened to me once on an MGA, and subsequently on a Cobra 289 Replica I had for two glorious years in the early 2000's.
Coil gets hot after 15 / 20 mins or so, starts to fail, giving the same effect as the thing running out of juice. Let it cool down, and it will go well again until it gets warm.

Change it for a known good coil, and drive, that way you'll know quickly if you have a fuel delivery problem.

Steve
 

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Discussion Starter #12
Hello, an update and still work in progress it seems.

I've replaced the rear fuel filter and installed a replacement fuel pump from Centerline. No change.

Installed a new 12v coil and no change.

If anything the car appears to be running worse now, misfire happening quicker than before, doesn't require 10mins of driving around to kick in. Also idle seems rougher with possibly the engine running richer based on smell after turning it off.

So next steps I'm considering - a compression check and checking the timing.

Then go back to the ideas 1 & 2
1) The approach of Michael Keith as it does have the Fireball Ignition.
http://www.alfabb.com/bb/forums/gt-1...tml#post416576

2) Looking at the Barometric Compensator as discussed by John Stewart in the SPICA FI Pump sticky.

For Alfar7 - I don'k now how to measure the pressure at the SPICA. Will have to learn this.

For 1900CSS - It had a Marelli coil and a Crane Fireball Ignition. The Crane Fireball XR700 remains but the coil I've just replaced with a standard OEM one to test if the coil was the problem. I've not looked at the condensor. I don't understand how that would produce this as the car does not have A/C.

Thanks to you all for your responses.
 

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I've not looked at the condensor. I don't understand how that would produce this as the car does not have A/C.
That's actually pretty funny. I assume you are responding to 1900CSS's suggestion: "If you have a point type distributor, replace the points and condenser,.... " The word "condenser", in this context, means the capacitor wired in parallel with ignition points. Not an A/C condenser. Your Fireball system has no points, so it has no condenser (= capacitor).

It had a Marelli coil and a Crane Fireball Ignition. The Crane Fireball XR700 remains but the coil I've just replaced with a standard OEM one to test if the coil was the problem
Different coils have different primary resistances. And you can't necessarily interchange them - the Fireball probably needs a coil of a specific resistance. The Marelli and/or "standard OEM one" may not match that.
 

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I've had one of these xr700 on my car since the late 90s, actually an Allison from before Crane bought them, it's just fine.

But I don't understand from the description when this misfire started. Did you just buy the car and it's always had it ?

The trigger phasing is part of the installation instructions, so it should be done. If you weren't involved in the trigger installation or if it was from before you bought the car, by all means, take the distributor out, and go through the full installation procedure to make sure it's ok. You may simply have hold-down screws for the trigger loosening or something "silly" like this. Also you can make sure the wires between trigger and control box are ok and well connected.

FWIW...
/Neil
 

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The XR700 unit is designed for ballasted ignition system, a needing 1.6-ohm coil and 1.6-ohm ballast resistor. The electronic unit normally runs on 6-7 volts and tolerates a momentary 12 volt input during crank starting (same as the ballasted ignition coil).
From Electronic ignition, Crane/Allison XR700
 
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