348 Start problem... or not?

First thought would be fuel pump related. Cheapest, lowest effort next option would be to try some MMO (Marvel Mystery Oil) in the fuel in the next 2-3 tank fills. I've had a similar issue on my 95 F355 where it wouldn't start on 1st attempt but always started on the 2nd. I ran some MMO through it and it hasn't been an issue since.

 

MMO is indeed a light oil with both cleaning and lubrication properties - its been around forever, since the 1920s. If your fuel pumps and filters are new then maybe the injectors might be the next thing to look at? It would be a little odd that they'd work well enough when the engine is running but not on a cold / hot start situation though. When my car was exhibiting the issue it was definitely a cold start 1st try problem. Neither a 2nd try nor a hot start was problematic.

 

If such behaviour was normal (for the model, not just to a particular car) when the car was new, it would be normal after 30 years. It is true that many 30 year old cars have faults and problems, but that doesn't make it normal. There is no reason why car without faults wouldn't work as new.

Considering the debugging, 348 has 2 distinct fuel systems. If one pump fails, the car will fire up with 4 cylinders. If it fires up with all 8 every time it finally fires, I'd start looking elsewhere. It also has 2 distinct ECU's and ignition systems, so the same goes for those. Therefore I would probably start by checking all the ground points / cables and the + -side connectors and junction points, concentrating at first on such connections that can affect the both sides of the engine.

If it does fire up with 4, then I'd concentrate on the non-running side first.

 

Fuel pressure regulators . They go bad insidiously.

You need to hook up a fuel pressure test equipment, or get a shop experienced in 348 s to do it .

 

Mine starts first try, every time. Like it should.

 

as above should start first time everytime. even my previous classic triumph of 60 years, started everytime!

clue above, 348 has twin systems so to not start it needs to be either in part of the system that isnt or you have a very unusual failure mode affecting both sides at the same time.

I would do two things, 1) check wiring/fuses/relays/earths from the battery and ignition switch working your way towards where the system splits in two. 2) whilst it doesnt sound like it from the video as it tries to start; do you have an immobiliser/alarm? these are a great source of intermittent trouble. unless I need them for insurance I always take them out.

if all the above checks out, if you haven’t replaced them change the crank case sensors, cheap and are also an annoying source of faults, but usually just one bank

 

when it doesn't start, what does it do? just cranks and cranks? or eventually slowly sputters to life?

sjd

 

There is nothing wrong with your starter. When it sounds like turning faster, it is when the engine is "trying" to fire-up but it doesn't. The problem is elsewhere.

You said you replaced "crank case sensor". There are two of them, which one did you replace?

 

Correct but, if the sensor gaps are incorrect, they may cause somewhat poor signal at low RPM (when cranking) causing difficult start but causing no problem when the engine is turning faster (stronger induction in the sensors). What gap did you set the sensors to?

 

You should check the gaps using non-magnetic feeler gauges. The acceptable gap is anywhere between 0.35 and 0.90 mm while, at the same time, having as little gap difference as possible between the two sensors.

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I haven't viewed the video but as someone else has said, fuel pressure regulators is where my mind goes. Or possibly the check valves in the pumps... Either way check the fuel pressure.

 

There must be many respectable independent Ferrari ( and “ supercar “ ) dealers with shops in Belgium/ NW Germany .Totally familiar with those FPR issues , equipment to accurately diagnose before throwing parts ( like you have ) and fit working solutions .

 

First simple test for FPR's, as they tend to leak from the suction hose.

1) Find a friend, 5cm of wire and 2 flat connectors or about 6 meters of wire, 2 flat connectors and a closing pushbutton.
2) Put the connectors to the ends of the wire and if you have a long wire, the pushbutton in the middle
2) Dig out the relay panel on the passenger footwell and locate fuel pump relays
3) Take out one fuel pump relay
4) Take out the FPR suction hose from plenum side and put it in a bottle
5) If you have a friend available, tell them to put the wire in place of the relays connectors 30 and 87 just for a small moment, like 1-2 seconds.
5) If you have a long wire and no friend available, put the wire in place of the relays connectors 30 and 87 and take the button next to you near the engine bay (ensure the button doesn't have any clear connections that could hit the chasis of the car and do not keep the button close to the FPR hose in case a cheap button decides to spark) and push the button for a little while. The pump will take a mentionable amount of current, which will kill a cheap button quite soon, but you should be able to see results in 1-2 seconds.
6) You should hear the fuel pump running (pump test) and you should NOT see gasoline coming from the host to the bottle (FPR test)
7) Remove the wire, put the relay back and put the suction host back to it's place
8) Repeat steps 3-7 for the other side

To actually measure the fuel pressure, you'll need a fuel pressure gauge. With the engine not running and the fuel pump running you should get 3 or 3,8bar measurement on the gauge depending on the fuel system of the car.

FWIW I still don't think your problem originates from the FPR as my mind can't get around how faulty FPR could make those symptons on 348, but it doesn't hurt to know how to check them and it doesn't hurt to know they are ok.

Note: be careful when playing with gasoline, as it's quite highly flammable. You do NOT want any sparks nearby. Also be careful when playing with electrics, especially if they are unknown territory for you, as they can spark and make very nasty faults if handled wrong (eg. you put a connector to a wrong connection when mimicking the relay with a wire). If gasoline or elecrics are not familiar for you, it might be a good idea to find a friend who is familiar with them to ease up the DIYing and getting familiar.

 

Yep, as far as I know the most usual way for FPR's to break is to start leaking to that particular hose.

I disagree on the level of unfortunate, as I still think there's (at least) something else wrong with the car than the FPR's. Now you can move forward from the FPR's to find out other possible reasons.

Gathering from this thread, I'd continue next to debug the immobilizer by finding out how it prevents the car from running and check if bypassing that mechanism helps. Unfortunately I don't have any magic wand for this one, I myself would most probably have to find the immo unit from the car and follow the leads connected to find how it works. For me it sounds the most reasonable culprit, as such system has to be wired to stop both sides of the engine from working.

After that, I'd probably continue with either checking the crank sensor signals (they can be measured with oscilloscope from the ECU connector, but for that you need an oscilloscope) or by going after possible ground or power connecting problems.

By the way, you mentioned you have changed the crank sensors. Was there a reason for that and what was it? Was it this fault or something else? If it wasn't this fault, was this fault active before changing them at all and/or did it start or go worse after changing them? If the problem started or got worse when changing them, I'd shift the gap checking and signal measuring to be the next step.

 

I don’t think the FPR are a binary item in the sense they either function 100 % or the plenum drain gets leaky .
They fail in many modes the above being one . Including intermittent when hot , which hasn’t been tested .

There’s a reason a 40 yr Marenello trained U.K. tech regularly switches them out and retro fits these on all 348 s he’s looking after .

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3.8 bar on this 94- 320 Hp euro modal .