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Cat fire question

Discussion in 'Technical Q&A' started by Morrie, Oct 30, 2004.

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  1. Morrie

    Morrie Karting

    Nov 4, 2003
    207
    Sarasota/Asheville
    #1 Morrie, Oct 30, 2004
    I just had a major service on my 83 308QV which is equipped with with two small cats. After the service the car became hard to start after running and then sitting for a few minutes. The tech suggested it was injectors leaking down, or the check valve that prevents fuel from leaking back out of the lines. He suggested running a full tank with a double dose of injector cleaner to see if that will fix it first.

    He richened the misture considerably to see if this would help, but it didn't. It is still very hard to start and is running so rich that it stumbles and dies at idle so I advanced the idle set screw to make it idle at 1,000rpm.

    Now I have two concerns:

    The slow-down lights don't work and until I get them fixed, I don't know if the much richer mixture is a potential cat fire hazard.

    Secondly, I'm not sure just how much to lean it out after I get the problem fixed either with new injectors or check valve. I think the mixture was advanced three flats, but I'm not sure. I figure I'll go back two flats, but realize how risky this is if I get it too lean.

    Can anyone offer some help?
     
  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,932
    30°30'40" N 97°35'41" W (Texas)
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    Steve Magnusson
    #2 Steve Magnusson, Oct 30, 2004
    What version '83 308QV? (And why does your profile say 328?)

    If your '83 is a K-Jetronic with Lambda then a mixture tweak will affect the (open-loop) cold-running, but it's not been widely reported as something changed to "fix" a hard starting problem IME.

    I can't really give specific help for your problem, but I'm skeptical that a mixture tweak would be the fix for any closed-loop K/KE system exhibiting those symptoms.

    IIRC, the '83 QVs have quite a few extra gizmos for extra air and fuel tweaks at cold-start, but for a warm-restarting problem on any K/KE system I'd definitely confirm/deny the suppy side fuel pressure behavior before resorting to (mis)tweaking the open-loop AF ratio -- JMO.
     
  3. thecarreaper

    thecarreaper F1 World Champ
    Silver Subscribed

    Sep 30, 2003
    18,121
    Savannah
    #3 thecarreaper, Oct 30, 2004
    excess fuel in the exhaust will toast the O2 sensors and ruin the cats. find another tech as this does not sound right to me. your cats may already be clogged, and the excess fuel is going to make it much worse. if you do any of your own work, start it and drive it around the block with the exhaust off at the flange where the cats start. this will tell you if the cats are dead and the problem is there and not in the engine / fuel system.
     
  4. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    37,288
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    Brian Crall
    #4 Rifledriver, Oct 30, 2004
    If your problems started coincident with the service I strongly suggest considering something that was done at the service. Suggesting that an injector problem happened just after servicing was either wishful thinking or poor diagnostic skills on their part.

    If you ever watch the changes in fuel mixture on an exhaust analyzer while adjusting the mixture screw on a Bosch CIS system you will realize it is way to sensitive to do that adjustment any other way.

    If in fact this problem started at the time of the service I think your shop owes you a diagnosis, then and only then can a determination be made as to who should be responsible for resolving it.
     
  5. Morrie

    Morrie Karting

    Nov 4, 2003
    207
    Sarasota/Asheville
    #5 Morrie, Oct 30, 2004
    I will update my profile to indicate that I got rid of the 328 and acquired a 308. I welcome all the responses to my query.

    How do I determine what inection system my QV has? It has a December 83 manufacture date.

    I drove the car for the better part of two days before buying it and turning it over to the shop for the service. I never had any trouble starting it hot or cold.

    One of my problems is that the work, which was promised in a week and a half, took a month and by the time I was able to retrieve the car I had to be on the road and couldn't insist that the shop keep it and make it right. All I wanted to do by then was to get it away from them. There were numerous other things that were not done the way I requested. Unfortunately I was 200 miles away and had a hard time getting answers about what was happening.

    When I drive it now, the mixture is so rich that my eyes burn. At this point I'm afraid to drive it any further for fear of toasting the cat or damaging the engine. I watched the tech richen the mixture what I think was three flats, but when I asked how to restore it to original he told me to turn it no more than two.

    This now has me really concerned.
     
  6. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
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    #6 Steve Magnusson, Oct 30, 2004
    Morrie -- I was in error. The (2-cat) '83 QV has the open-loop K-Jet injection system, whereas the (1-cat) '84-'85 QVs have the closed-loop K-Jet with Lambda (but I'd still say there are better things to check first than tweaking the mixture as the primary "fix" for a warm-starting problem).

    To check out your '83's lineage, decode the VIN per the information given here:

    http://www.ferrariclub.com/faq/vin.html

    You can also download the various 308QV OMs at www.owners.ferrari.com and compare the components described in the "injection system" section of the OMs to the hardware on the car (they give a suprising amount of good tech info IMO).
     
  7. Morrie

    Morrie Karting

    Nov 4, 2003
    207
    Sarasota/Asheville
    #7 Morrie, Oct 31, 2004
    Steve,

    A knowledgable friend is convinced that it is the check valve. He also believes that the adjustment I described to him only affects the idle and suggested that I couldn't get in too much trouble by leaning it out. Does this sound consistent with what you know?

    The lesson I learned is to never leave a car with a shop that is a long way away. I made two unannounced 400- mile round trips and in both cases found that what I was being told was not being done.

    When I do a big-ticket deal with a shop in the future, I will get a letter from them spelling out exactly what will be done and an approximate completion date.

    I have to rely on mechanics for work I would normally do, since I live in a motorhome and trailer the car. I have no place to do any serious work on it.
     
  8. tbakowsky

    tbakowsky Two Time F1 World Champ
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    Sep 18, 2002
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    Tom
    #8 tbakowsky, Oct 31, 2004
    Be sure you warm up reglator is work propperly. By what your saying this is a typical sypmtom. But check a fuel pressure first an from most. Cold Warm and hot then rest pressure. This will tell you the most.
     
  9. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
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    #9 Steve Magnusson, Oct 31, 2004
    Morrie -- Couldn't agree with you more that a long-distance relationship just doesn't work out well (I did that with my TR major last year thinking I was saving money and have come to regret it).

    IME setting up a K-Jet is about getting the right amount of air flowing into the engine to hit a target RPM both with the (idle) air-bypass screw fully closed (air entering the engine thru the throttle path only) and then with the air-bypass screw opened (air entering the engine thru the throttle path + the air bypass circuit) {and having the mixture set close enough so that it runs under those two conditions} -- the mixture screw is then set at the final RPM condition to achieve a desired %CO at the inlet to the cat.

    Doesn't sound like the artificial enrichment is helping your restart problem anyway so I'd undo/correct, and if "3 flats" means 1/2 turn of a hex wrench that is BIG tweak so even with your opening the air-bypass screw you are probably over-rich still (although I thought the nominal idle RPM target was 1000 RPM?).

    For looking deeper into your poor restart behavior, you've probably got to start measuring/verifying the pressures (supply, supply after shut-off, and control) as Tom said. Have you checked that all of the other associated gizmology described in the OM injection section is reconnected after your service?
     
  10. brian.s

    brian.s F1 Rookie
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    Nov 3, 2003
    3,809
    Midwest
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    Brian
    #10 brian.s, Nov 1, 2004
    I would agree that this needs an experienced tech to look at and diagnose. The system is very sensitive and should be adjusted in small increments, and checked each time. It would be easy to destroy cats and O2 sensors.

    Certainly would seem that the time is right to start at basic fuel 101. Fuel pressure, lamda operation et al.

    best of luck, Brian
     

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