308 defect has boggled experts. Help !!! | FerrariChat

308 defect has boggled experts. Help !!!

Discussion in 'Technical Q&A' started by gary308gtb, Jan 15, 2004.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. gary308gtb

    gary308gtb Rookie

    Oct 9, 2003
    My 308 has been with a expert mechanic for 2 months ! He couldn't fix the problem with the car, so I brought it in to the service department of the Ferrari Dealer in my country. The car has also been with them for about 2 months !

    The main problem is : when I drive the car, at any gear from 1000 to around 4300 rpm it runs great ! However, at any gear, if I drive the car at 4500 rpm and up, i experience sputtering with the engine like it is starved for fuel.

    What has been done : the timings have been checked and are ok, the distributor settings have been set properly and are ok, they thought my fuel pump was not delivering fuel at high rpms, they replaced it with a new fuel pump and the problem was still there at high rpm. The spark plugs have been checked and are still ok. All the carbs have been cleaned thoroughly.

    If you drive the car at low revs, you won't even know that there is a problem. The engine runs smoothly at all gears at low rev (4300 and below).

    The Ferrari mechanics have hit a wall on this matter. Their last recourse is to check and maybe replace the high tension wires.

    I'm kind of worried that it'll never get fixed. It might take a year.


    (MY CAR IS A U.S. VERSION 1978 308GTB)

  2. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    San Antonio
    Full Name:
    Russ Turner
    The usual suspects:

    plug extenders (!)
    fuel filter

    would check these.
    good luck!
  3. jbrosseau

    jbrosseau Karting

    Nov 26, 2003
    Full Name:
    joe brosseau
    start with the easiest most simple things and work your way to the hardest. remember a engine needs only 3 things to run right.
    so the timing as well as advance have all been set up properly?
    air is usually not the issue.
    so my best guess has to do with the fuel system. carbs are clean, but have they been rebuilt? could it be a carb metering issue? can you find out what the AIR/FUEL ratio is on your car from idle till the problem occurs?
  4. rudy

    rudy Formula Junior

    Jan 13, 2004
    Los Angeles California
    Full Name:
    Rudy Hassen
    Excuse my ignorance, but if all those things have been checked, an exhaust restriction may be the culprit. I can't believe that testing with "scopes" doesn't reveal anything. It can't be THAT complicated.
  5. jbrosseau

    jbrosseau Karting

    Nov 26, 2003
    Full Name:
    joe brosseau
    i have to say rudy's blocked exhaust theory is a good one. the catalytic converters can come apart internally and work their way into the muffler. when i gutted my cats on my 79' 308 there was alot of cat material in the muffler. if enough made its way in their it could cause issues when exhaust flow got too great.
  6. atlantaman

    atlantaman Formula 3

    Mar 31, 2002
    Roswell, Georgia
    Full Name:
    plug extenders being cracked and allowing grounding caused a similar problem on my car

    But it would also be VERY WISE--to install a wideband EGR sensor and see if you are getting lean or rich inthe high RPM range--the more infor the better for a good diagnosis.
  7. jmillard308

    jmillard308 F1 Veteran
    Owner Silver Subscribed

    May 29, 2003
    Perth West Oz
    Full Name:
    John Millard
    Sounds like fuel flow rate - check at carbies and if a problem, work back through the fuel system.
  8. jbrosseau

    jbrosseau Karting

    Nov 26, 2003
    Full Name:
    joe brosseau
    it would be great to know the fuel pressure's from idle, off idle, to WOT.
  9. TOM B

    TOM B Formula 3

    Jul 24, 2003
    Orange County, NY
    Full Name:
    Thomas Buckley
    I vote for dirty fuel filters. I think there are two on the 308. You might also check for a blocked or crimped fuel line. A high RPM miss may also be evidence of a bad coil. Plug extenders are another easy thing to check and a cheap thing to replace. Even a tiny pinhole can cause enough arcing to give a high RPM miss.

  10. gary308gtb

    gary308gtb Rookie

    Oct 9, 2003
    After reading all your suggestions, it seems that we have overlooked quite a number of things. Will definitely follow all your advice and give the Ferrari Mechanics a print out of your advice.

    Will see what happens. Will write a new thread as soon as we fix the problem.

    I feel so relieved that there are so many knowledgeable Ferrari enthusiasts in FerrariChat. Thanks

  11. joeyy

    joeyy Karting

    Nov 11, 2003
    long island
    Full Name:
    fuel delivery seems quite possible. check w/a flow meter, it won't bethe first time a bad fuel pump was replaced with another bad one. also i am wondering how old the coils are? they can also cause the same problem. at highet rpm they send a weaker spark.
  12. Mike Florio

    Mike Florio Formula Junior

    Jun 19, 2003
    NW Rural Nevada
    Full Name:
    Mike Florio
    All great suggestions above. I would recommend four more places to look as well:

    (1) Fuel filters on the carb inlets, a cylindrical screen strainer between the inlet fitting and the needle valve.

    (2) Needle valve and float operation

    (3) Vacuum line from the front bank of carbs to the charcoal cannister.You can just plug this line and test the engine.

    (4) Vacuum circuit for brake system. Draw a vacuum on it and see if it holds.
  13. gerritv

    gerritv Formula 3

    Jun 18, 2001
    St Catharines
    Full Name:
    Relatedx to the fuel flow being a potential problem, this past summer my car was stuttering a lot once it was past 1500 RPM. Cause: the fuel hose from pump to filter was slightly too long, it then kinked due to the 35C outside temperature. I shortened the hose a bit and all was fine.
  14. tbakowsky

    tbakowsky F1 World Champ
    Consultant Professional Ferrari Technician

    Sep 18, 2002
    The Cold North
    Full Name:
    Check the points!! If the points are out of adjustment or just plain worn out that would for sure give you this problem. If your car has the 4 sets of points(2 per distributor) make sure that the mirco switch by the carbs is working to shut off the other set points once it's off idle.

    All other suggestions are excellent. always always start with the basics!!
  15. mikeg

    mikeg Rookie

    Nov 3, 2003
    If the plug wires are old, change them....Its a good bet
  16. robertgarven

    robertgarven F1 Veteran

    Feb 24, 2002
    Ventura, California
    Full Name:
    Robert Garven
    new ferrari mechanic.....
  17. flashman

    flashman Formula Junior

    Jan 5, 2004
    Star Valley, Arizona
    Full Name:
    William Rappaport
    I had that same problem, pulled the cats off and found the remains had turned to what looked like heavy sand. When the car was run at high speed, this would block up the internals an cause the same sputtering. I was able to take care of this before it really turned into a major problem by removing the catalytic converters and cleaning everything out.
  18. ferrarifixer

    ferrarifixer F1 Veteran

    Jul 22, 2003
    Full Name:
    Phil Hughes
    Is it only happening under load...ie, if you rev the engine while parked in neutral, does the same sputtering happen, or do you need to be at wide throttle openings under acceleration??

    If it is a load only thing, then putting the car on a rolling road while connected to exhaust analysis and ignition scope is the quickest way to a diagnosis.

    I still reckon a decent mechanic is your main problem. Dealers are really only geared up for newer cars, the older stuff needs boys from the old school to take a look........
  19. Michael Aguilar

    Nov 28, 2003

    I was at the ferrari service center this afternoon , I think they overlooked the cam timming of cylinders 5 to 8. I believe this where timmed using the timming marks of cylinders 1 to 4. I ask if they adjusted the cam belt timming , they said no. So i'm hoping that's been the problem all this times. The previous mechanic timmed both banks using only the cam timming mark of cylinders 1 to 4.
  20. ferrarifixer

    ferrarifixer F1 Veteran

    Jul 22, 2003
    Full Name:
    Phil Hughes
    That is the correct way. All four cams are on their marks when cyl 1-4 are TDC.

    The 5-8 cams will be 45 cam deg or 90 crank deg advanced from their marks if 5-8 is put on TDC.
  21. Steve King

    Steve King F1 Rookie

    Feb 15, 2001
    If this has been a problem for 4-5 months then I think we all question your mechanics capability. But beyond that the carb motors are quite simple. As stated by the answers above there are a few things to consider but 1st you need to give us all of the info of the car and what was done. So here are a few questions that we need to unserstand.
    1. year / model ans. 1978 308 GTB US
    2. Miles from last major service and what was done
    3. Cat or non cat (was cat removed)
    4. Is emmission system in tact or removed
    5. Twin distributor or single
    6. Points or electronic ign. (single point or dual point) what type electronic conversion if done.
    7.Cap/rotor/SP wire condition and verification (ohm value check)also were each extenders checked /verified for leakage
    8.Distributor advance curve checked and verified up to max rpm
    9. Timing verified at idle and WOT
    10.Carb balance at idle and 7000rpm
    11.Vacuum leak check
    12.Fuel pressure check at idle and WOT
    13.Air cleaned (is it clean or dirty)
    14. Fuel filters changed
    15.Spark plugs REPLACED and gapped
    16.Compression check
    17. Fuel octane
    18. Coils condition and check for value
    19. Air/fuel mixture and CO reading
    20. Coil resistors verification
    These are a few things that I would check and they are not in any specific order. Also check all electrical connectors and capacitor values.If all of this was checked and verified and you still have the problem then I'm at a loss. Please let us know how you make out.
  22. Michael Aguilar

    Nov 28, 2003
    Gary's problem started with just a simple cam belt change. Prior to that car was running fantastic.
  23. rudy

    rudy Formula Junior

    Jan 13, 2004
    Los Angeles California
    Full Name:
    Rudy Hassen
    Oh well, he's got screwed up cam timing, or some device driven off the cams is off by x number of degrees. Assuming nothing simply failed during the fix. Time to see another mechanic. After that length of time, the first mechanic should be on the hook for the second mechanic's bill if he finds the problem. If a mechanic makes a mistake or can't find a problem, he doesn't get until infinity to correct the situation. That's not loyalty...that's nuts.
  24. robinh

    robinh Formula Junior

    Jan 3, 2004
    Cambridgeshire, Engl
    Full Name:
    I had a similar problem to this on a Merc. Took it to have a general service and afterwards it was dreadful. After three months at the main dealer it turned out to be the tank of fuel I had bought just after the service - drained the tank and it went away. Have to say all the test Merc did showed nothing and they changed almost everything before at last deciding the fuel could be the only thing left to change
  25. gary308gtb

    gary308gtb Rookie

    Oct 9, 2003
    Hi Michael, Hi Ferrari Fixers & all the helpful Ferrari guys,

    When Michael Aguilar visited the Ferrari Service Shop, he mentioned to the mechanics that the cam timing of cylinders 5 to 8 should be checked and adusted since they thought they already had the correct timing.

    This led the mechanics to read the workshop manual for the 308. And to their absolute astonishment, they saw for the first time the numbering of the cylinders in a simple diagram, and they immediately realized that they had been timing cylinders 8 to 5 instead of 5 to eight !
    They had inverted the way they they have been timing cylinders 5 to 8 !
    They said that they felt so stupid about overlooking the numbering of the cylinders.

    Well, as of today, they adjusted the cam timings and the ignition timings. So the problem of sputtering, backfire, and fuel suffocation at 4500 rpm up has been lifted. At idle, the engine revs smoothly until 6000 rpm. Unfortunately, they have yet to test drive the car.

    I can't believe it myself that all the mechanics who have timed the car, confused the 5 to 8 cylinders with the 8 to 5 cylinders.

    I hope this is the REAL CULPRIT which had caused all the performance problems at 4500 rpm and up.

Share This Page