Have had a difficult time starting my 348 when hot occasionally. Referenced the old posts regarding this issue and the 348 Technical Primer. My Ferraris symptoms appeared to fit the faulty Pressure Regulator problem. Purchased 2 Bosch Pressure Regulators 0 280 160 731 as recommended. That was my 1st mistake. My 348 spider uses Bosch Pressure Regulator 0 280 160 738. The difference between the 2 is the 731 regulator uses a rubber hose clamped with a hose clamp. The 738 as used on my model uses hard compression type fittings. Now I am not positive the Fuel Pressure Regulator is at fault. My reasoning is as follows: No gas on the vacuum side. Good. The fuel rails had gas as far as I could tell. Not dry. Good. This leads me to believe the cause could be elsewhere or still with the regulators. An odd feature when difficult to start. If I feather the gas the car will generally fire after a few attempts. If I dont touch the gas, no go. 90% of the time the car starts with no issues. The problem does appear to be getting progressively worse. Opinions and related experience welcome.
I'd think that you'd want to find out if the hard start is from a fuel/air mixture or spark problem. The easiest test is to start your 348 when the motor is cold, drive until it is hot. Turn off the motor, and then immediately start it back up again (once the motor stops turning). If your hard start problem is from a leaky fuel injector or failed fuel pressure regulator, your 348 will restart easily because you haven't given the leaky component time to leak (much). Another mixture test is to spray starter fluid into the air intake box with the motor off (but when the motor is still hot). You also might open your throttle body air bypass valves. These valves have a screw that can be opened to allow more air in for starting and idling, which may be needed over time as various passages accumulate gunk. Each tb has one screw just forward (toward the cockpit), yet still on the side of the tb. Just use a 9/16" open wrench to loosen the holding nut. Once the holding nut has been loosened you can then turn the air bypass screw with a flatblade screwdriver. First, count the clockwise turns to fully close this air bypass/screw. Then open it up counter clockwise that much plus 1 full turn. Do the same for the tb on the other side of the engine. Also, insure that they are turned out/open the same amount. Then tighten the 9/16" holding nut down on each tb while holding the idle air bypass screw steady with a flatblade screwdriver. If all of the above tests fail to easily start your 348, then you should check for spark by pulling one plug and laying it on top of your engine intake plenum. Watch it for spark while someone else turns your ignition key. These tests should help you decide if you have a fuel mixture or spark problem. Of course, the problem could also be a "Flywheel Grease" issue, but do the above tests first.
I had a hot start problem on my 348. i'd run for a while shut it down 20 minutes later it would be a bear to start. Multiple attempt, and long cranking times on the starter. i'd start just fine cold, or if you restarted the car just after you shut it down from hot. like if you were filling up with fuel, it's start back up fine. both of my regulators were junk, leaking fuel in to vacuum lines etc. i could get the car in the failed condition reliably every time just be running it for a while and letting it sit for a while before restarting.... regulators were the fix. that was and easy hot start fix on the 348, let me tell you about the hot start problem on my 328 when you have some time )
had this same issue on the Mondial T/348 engine. Ferrari installed a 'booster' kit--about $80-- that boosts the current from the key to the starter solenoid: no problems with hot starts since and it's been over two years.
That's a good point. If the *starter* isn't turning, the ignition circuit needs checking. And if the starter is turning but the motor isn't firing up, then you need to check for fuel mixture and spark.
Read this if you haven't already. I did this upgrade and have had no problems since. http://www.ferrarichat.com/forum/showthread.php?t=160866
Thank you all, NoDoubt. I performed the hot start test as you detail and as is well documented in the 348 primer online. The car fired fine when I tried to start immediately after shutdown. I will repeat the test to confirm. I don't think the problem is power to the starter. The car appears to crank fine. Not labored or slow. The car does not appear to exhibit any of the "Flywheel Grease" issues from what I have researched. No odd rattles or sounds. Clutch engages fine etc. tamf328. That is why I suspected the Fuel Pressure Regulators at the onset of the problem. When I checked they had no leaks into vacuum lines and appeared to hold fuel in the fuel rails. Perhaps they are weak and the pressure is inadequate??? The symptom I find telling is the fact that the car will start when the problem arises by "Feathering" the gas. I just don't know what it tells me! Anyone have a good source for the Bosch Fuel Regulators 0 280 160 738? My limited search has yielded no direct suppliers.
FPR's are just the most common fuel rail part to leak. Fuel injectors can also leak. Your successful "restart test" tells you that the problem isn't a spark or flywheel grease or starter motor problem. This narrows down your hot start problem to any part of the fuel flow/mixture system that can leak pressure or block flow, from Fuel Pressure Regulators (FPR's) to fuel injectors to fuel pumps to fuel rails to return valves to fuel lines to fuel filters, etc... OR... ...To anything that can block air flow (e.g. clogged throttle body bypass valves, clogged air filter, etc.). So based on your above successful restart test, I'd suggest next opening up your throttle bypass valves (especially considering that when you open/feather the throttles by hitting the gas pedal, your 348 will start even when hot - because that's what the bypass valve does is essentially open the throttles just a bit).
when you start the car from stone cold does the idle act correctly. i mean are the rpms up and then settle to some static value like 1,000 rpms? when you finally get the car started from a hot start problem does it idle correctly where is should, like around 1,000 rpms? my car would start right up if you restarted it fairly soon after it was hot... the regulators were obviously the problem by the leaks. You can find replacements from any bosche supplier, just have to call around. got mine here, http://www.t-hoff.com/ something like $68 ech.
