Mondial t left side not firing

Maybe it's a blown relay?

I'm totally guessing at this point.

 

http://www.ferraridatabase.com/The_Downloads/Manuals_Workshop.htm

 

Motronic uses a combined injection+ignition ECU so they are just sort of abbreviating the name/function of that relay (i.e., it serves the ECU that controls both the injection and ignition functions).

The schematics in that Mondial T WSM are particularly user hateful, but they (pages 190 and 191 of 652) indicate that the fuse (with the brown? wires) that you show as being blown in the photo is for the fuel pump -- not the Motronic ECU. Can you please confirm the wire color on the 7.5A fuse that keeps blowing (that current rating seems kind of low for a fuel pump), and the wire colors and current ratings for the other 2 fuses in that same area?

 

The 7.5A fuse value is probably OK. Usually, EFI fuel pumps run in the ~5A range (and the fuse might be selected to be 2X that value), but I have no exact current data for your fuel pumps so the current might be a little lower.

However, the fact that it blows is a terminal condition for operation, and, based on the horror stories/photos posted here about 348 fuel pump internals falling apart and clogging, could be your problem.

Can you clarify how many fuses & relays you have associated with each ecu? That schematic shows 2 relays (one for the Motronic ECU and one for the fuel pump) and three fuses (fuel pump, Motronic ECU, and O2 sensor heater), but, if you had a 2.5 Motronic without O2 sensors, you'd only have two fuses with each ECU. Also, the schematic shows that that fuel pump fuse should have two large MB (brown/white) wires, but little differences like one wire actually being M (brown) and one wire being MB (brown/white) are not uncommon to find. However, IME, F has a history of using brown (or beige) as the base wire color for the fuel pump operation so I'm fairly sure that that's the fuel pump fuse, but, if you can give the wire colors on the other fuses, that can be another way to be a little more certain about things. The WSM schematic for that side shows:

Fuel Pump Fuse = MB (brown/white) wires
Motronic ECU fuse = RN (red/black) wires
O2 Sensor Heater Fuse (if present) = S (pink) wires

 

HURRAY!!! Someone who knows what they are talking about, because I sure didn't know where to lead this guy anymore.

Rock on Steve!

You have a VERY good point about the fuel pumps, and that never even crossed my mind. I don't know for sure if the Mondial T has the same fuel pump set up as the 348 but, ....... I think these threads could help him out with some.

Page #2 of this thread http://ferrarichat.com/forum/showthread.php?t=193188 has the fuel pump removal from the tank.

And here is the thread for the fuel pump once it's out. http://ferrarichat.com/forum/showthread.php?t=224988

 

I just checked the 348 WSM and that shows a much more reasonable EFI fuel pump fuse rating of 15A -- Ernie, can you confirm that this is true?

If your Mondial T has been working OK with a 7.5A fuel pump fuse, but it now blows, that's a clear sign that things might be getting worse for that fuel pump -- but it would sure be good if someone else with a Mondial T (or someone who knows where they are shown in the documentation) could confirm/deny those fuse current values (I couldn't find anything for those fuses in the Mondial T WSM nor the Mondial T OM).

 

Wire colors on the other fuses (not relays).

I think the issue is more 20~25 years soaking in gasoline/gasohol -- not the mileage, but I'm still suspicious of that 7.5A fuse as the 348 seems to use a more reasonable 15A fuel pump fuse (see prior post). Do you know anyone else with a Mondial T to compare?

 

That sounds good, and quasi-confirms the functions of those other fuses to match what's shown on the schematic. But what are the current ratings for those fuses? Are they all 7.5A? (7.5A does seem a reasonable value for both the ECU fuse and the O2 sensor heater fuse.)

I see no downside to trying a 10A, or even a 15A, fuse for that fuel pump fuse as a brief test. This is where you'd really like to measure the actual currents that the fuel pumps are drawing during operation (and they do make inexpensive high-current ammeters that plug into that style fuse socket). For example, if your "good" fuel pump was drawing ~5A and the "bad" one was drawing 6~7A, I'd have no problem saying that you could just drop in the 15A fuse, and use as normal. However, if your "good" fuel pump was drawing ~5A and the "bad" one was drawing 12~13A, I'd say that, even if it worked OK with a 15A fuse in place, it is really not good anyway, and needs to be addressed. Of course, if the 15A fuse blows immediately, you know that you've got some sort of serious problem.

All JMO (and would like to have a comparison with another Mondial T and get confirmation that a 348 uses 15A for the fuel pumps) -- please proceed at your own risk

 

Yup 15A.

 

Mine was 7.5 amps. Blown but I replaced and have no problem as yet. Brown wire. In my case the brown wire under the passenger foot well was melted and I expect contributed to my problem. I rerouted the brown wire in the foot well around the plug and have had no problems since.

Work Shop manual, Page C3

 

Thanks for the confirmation Ernie. I still can't fathom how two electric fuel pumps, operating at the same voltage and delivering the same volume at the same pressure, could have such different currents (but perhaps its related to some inrush behavior difference).

Lino -- Don't really have anything else to add, but we'd always be interested in knowing what was the problem and what was the fix when you get it sorted.

 

Motronic, it's Motronic.

Anyway.

Try swapping it with the relay for the other bank and see if the "dead" bank jumps sides. That is if you have 2 ecu's.

 

YES!