Hi all, I am enjoying my 412 now for about a year and a half and really starting to know the car. One thing needs to be improved; the car starts really difficult with a warm/hot engine. Cold start is no problem, but when the engine is hot, and also after standing for half an hour to an hour it takes 4-6 times to start the engine. When I turn the key, the starter motor is turning and you hear the engine wants to start, I let go of the key, and the engine dies immediately. I was advised to give a little throttle during starting but it hardly improves it. One specialist told me it is due to the injection system which has no system for warm start, which I find difficult to believe. The K-Jetronic system was used in many cars, and I cant imagine they all develop this problem. Another specialist told me the reason is carbon deposit in the combustion chamber which increases compression ratio for which the K-Jetronic cant compensate. Does anybody know what the cause is and how to improve it. Thanks.
The easiest initial first test is to unplug the two cold start injectors during warm/hot restart just to make sure they are not overly-squirting. If no change in the (bad) behavior: The second diagnostic test is to measure the supply fuel pressures after engine shutoff when warm. They should not fall to zero quickly - should be something like 2.5~3 bar (IIRC) for at least 20 minutes. With two independent banks, the 12-cyl CIS cars are usually a bit more resistant time-wise to this fault causing an operational problem than the V8s (because, if one bank fails for this, it will still start on the other bank until both fail), but it's a relatively easy (and inexpensive) test to do. (However, with the two WURs connected together on your model, one of the fault modes that causes this problem could have a single fault affect both banks IIRC).
Easy to check; the accumulators have a drain which will drip fuel if the diaphragm fails. On later cars it's connected to a return line to the tank (at least, in the V8), which can be popped off to have a look
Most 12's (flat and V) have a balance hose from WUR to WUR which may bleed pressure from the good to the bad and effect both. Something to consider but when testing one bank at a time I suspect the bad bank would leak down more rapidly. Thats one disadvantage the K has vs the KE but thats about the only one I can think of lol.
I had a similar problem & mine turned out to be an easy fix. The start-up injectors should be pulsed when warm starting & mine were not getting power during warm start. There is a separate warm start relay that is like a blinker flasher but pulses about twice the rate & mine had a dried out electrolytic capacitor in it. Replaced the faulty capacitor and all good. Cheers Al
Another thing to consider is that the check valves on top of your fuel pumps are failing. They are responsible for holding fuel pressure in the fuel pipe loop that returns fuel to your tank(s). When you start from cold, the cold-start injector compensates for the lack of fuel pressure; they do not kick in when the car is hot. If you are running fuel containing ethanol in your car this will melt the rubber boots surrounding the fuel pumps that are immersed in the gasoline, one on each side of the tank. The emulsified rubber will eventually clog the check valves located on top of the fuel pumps. 412s have these immersed pumps, whereas 400s do not. I spent endless hours eliminating the above suggested issues to discover this was the cause of the same problem in my 412 you're experiencing.
Thank you all for your reactions. It has been a while but I want to pick up the issue again. In the meantime an expert has tested fuel pressures at various points in the system, and the conclusion is that the check valve on the left fuel pump is not closing properly, so the system does not maintain fuel pressure long enough. We have tried to remove the fuel pump from the tank but without succes. We could remove the ring that fixes the top of the fuel pump assembly to the hole in the fuel tank but then the fuel pump did not come out. It was stuck to the tank. Can anybody give some advise how to lift out the pump form the tank. Cheers.
I'd gently persuade it, it's got to separate: Ferrari 412 (Mechanical) - Fuel Tanks, Pumps, Lines: Page 010 | Order Online Eurospares
I'm facing similar problem where my car wont start. I have a 1977 Ferrari 400 (Automatic) and it has been almost a year since I started the car. Today, I installed a new Optima battery and tried to start it. Unfortunately there is ignition but the engine wont start. I have noticed that there is not fuel pump sound; could it be a bad fuel pump? if so, what will be an alternative? Kindly share your thoughts on what might be the problem(s) and possible solutions. regards,
I'm doubting the alternator. If so, where to get one? and any recommended interchangeable alternator?
Im assuming this is a carbed model for this year? I had a similar problem after not using for a number of months, one fuel pump had given up completely and the other no pressure. Replaced both pumps and now runs lovely. I'd check electrical supply to pumps first.
Al (or anyone else!), Do you have any photos of the warm start relay or the repair you made? My 1984 is also struggling when the car is warm, though seems to be getting worse over time. Interestingly, it now will refire a short time afterr shutting it off, but about an hour afterwards, it wont start (engine is still warm). Doesnt even sound like its attempting to catch. Once its cold again, starts no problem. Does this sound like the warm start relay to you guys? Thanks, Jason
It could be the scenario that after shutting off the warm engine, the fuel pressure drops quicker than normally expected. If there is an almost immediate re-start, no problems, the fuel pressure will still be high enough for the injection to do its job. But a longer delay for a re-start (say 15 minutes) brings the fuel pressure too low for the injection to work at warm temperature, therefore the engine is not getting any fuel and does not start. If this is the case, it usually means there is a leak somewhere along the fuel line (for example at a fuel accumulator).
For FI cars, just hook up some fuel pressure gauges. You can mention many possible causes here but it's al guessing. With some gauges attached you should almost certainly be able to track down the cause easily.
Your diagnosis seems to confirm what I suggest above. That the fuel pump will not remove is odd. I recall there is a rubber gasket underneath the ring at the top of the tank -- between the pump housing and the tank. Unlike the 400 series, the fuel pumps are immersed in the fuel tank, and if the problem you're experiencing is attributable to the same cause as in my case the rubber gasket may also have emulsified and has become an adhesive. I would recommend trying to remove the right-hand pump on the assumption it will be easier to remove and will allow you to inspect the fitting duplicated on the left-hand side. Indeed, if it is emulsification caused by ethanol, you should expect that the submerged gaiters on both pumps are shot and will need to be replaced. While you're at it, think about replacing the rubber hoses that connect the two tanks at their base as you will need to empty both tanks to remove the rubber debris. To state the obvious, be very careful will removal of gasoline and with any residual vapor. Best of luck.
In the meantime I have managed to remove the fuel pump from the tank and replace the check valve. Unfortunately this did not solve the problem. I loosened the pump assembly again and let the pump run to check for leaks. Petrol was spraying all over the place from the connections of the spiraled hose between the pump and the underside of the tank cover. Does anybody know why this hose is spiraled (absorb vibrations, cooling?). It is a firm PVC hose that lost all flexibility and was therefore impossible to close with normal hose clamps. We pressed on a new strait piece of PVC hose and assembled everything. Now fuel pressure remains high after switching off the ignition, and I am glad to say that the warm start is now working fine again. Thanks everybody for your advice. Cheers.