How To Change The Fuel Pressure Regulator on 348's

By Tmassey/tamf328 (edited by No Doubt)

DYI for Fuel Pressure Regulator on 1990 348ts
The following procedure was needed after diagnosing a hot start problem with the car after a complete warm up.

Using the test method suggested by No Doubt I found that shutting down the car and allowing it to sit for more than 3 minutes would take multiple attempts cranking the engine over to actually get it running. The problem existed even hours later of letting the car sit.

The problem was diagnosed by starting the car from cold, warming it up to operating temp and then shutting it down. The car would re-start immediately after turning it off...But if you waited as long as 3 minutes or more it became really difficult to get the car started again when hot. If you've got these exact symptoms, then you probably have one or more internally failing components.

Not only was it a pain the butt, it was very un-cool. Pulling the vacuum hoses off the vacuum ports of the fuel pressure regulators exposed raw fuel. There was raw fuel in both the regulator and the vacuum hose (small diameter) on one fuel regulator for one bank of cylinders.

Obviously there shouldn’t be fuel in the vacuum system. So a replacement part was needed.

Below you can see the fuel pressure regulator at the end of the screw driver pointer. It is mounted to the front top of the engine near the firewall. Vacuum line is on the indented part of the regulator next to the fuel rail.
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The pressure regulator has one inlet for fuel and is the black hose with the hose clamp on it, one vacuum line at the opposite end (small diameter) and one braided steel fuel line that feeds the injectors. You can see the blue connectors of the braided line.

1. Remove the negative battery terminal. Get a small rag or the like to catch any fuel that will drain when you break loose the connections. Place that under the regulator to stop dripping fuel.

**use only a flourescent or LED drop light. You are working with fuel! Fuel ignites! DO NOT USE AN INCANDESCENT HOUSE BULB FOR THIS JOB! **

2. remove the black electronic connector to the Idle Air control valve that is directly above the FP regulator, disconnect the small diameter vacuum line at one end of the regulator and the inlet fuel line after loosing the hose clamp (don’t remove the clamp just slide it up the hose).

You can see the idle air valve connector is removed, and the inlet fuel line is removed. At this point only a flat blade screw driver has been used.

3. On the side of the FP regulator there is a blue ended steel braded outlet line. Use two spanners (they are metric) and remove that line. I think a 17mm on the fuel line and a 14mm or 15mm on the regulator side. I can’t remember the sizes but all the wrenches I used were from a set. Nothing out of the ordinary.

4. Now if you’re lucky you will be able to loosen that large nut that secures the fuel regulator to the bracket. The nut is on the end where the rubber inlet fuel hose was connected. I couldn’t get that nut to break free, so to not waste any time or risk breaking something I continued as follows (step 5). If you are lucky enough to get that nut off, just skip the next few steps. Install the new regulator and follow on with step 8 you’re almost finished.

5. Now with an extension and ratchet with a 13mm socket and a U-joint remove the bolts that hold the bracket to the engine. DON’T completely remove the bolt that is attached to the wiring harness. Just lift it up and out of the way of the regulator bracket. This will facilitate assembly. Try not to drop the bolts in the engine somewhere….!
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Here you can see I’ve removed the complete assembly (bracket and regulator together). I have the closest bolt out of the engine but left the other on the wire harness just loosely installed.

Here’s the assembly, you can see where the braided fuel line was attached (threaded part) and where the vacuum line and inlet fuel line were attached.
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Here you can see I’ve removed the complete assembly (bracket and regulator together). I have the closest bolt out of the engine but left the other on the wire harness just loosely installed.

Here’s the assembly, you can see where the braided fuel line was attached (threaded part) and where the vacuum line and inlet fuel line were attached.
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Again the reason I took the whole assembly out was the retaining bolt, that large nut that holds the regulator to the bracket was so tight I was bending things trying to get it off in place. You can try it in place. If you’re lucky, you will be able to loosen that bolt and then you can just leave the bracket attached to the engine and remove just the regulator. Much easier of a job! See step 4.

6. I used a vice and a wrench (I don’t remember the size sorry) to remove the old regulator from the bracket. That sucker was tight!
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7. Now that everything is disassembled you can start reassembling the new regulator to the bracket just like the old one was. Just leave everything a little loose until the whole unit is installed back in the car. This way you can align things properly.


Here you see I have left everything loose on assemble. This is to make things a little easier to put back together.
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8. Now with the unit loosely in place the first thing you want to do is re-connect that braided fuel line that feeds the injectors. Now would be a good time to wrap one round (clockwise) of yellow teflon plumber's tape around the threads.

Everything is loose so we could get that fuel line perfectly aligned before tightening it. DON’T cross thread that sucker or it will leak for sure. That line should (start threading) go back on with your fingers, then snug it up with two wrenches. One wrench on the regulator one on the fuel line. Two wrenches will lessen the chances of you breaking a fuel line/fitting.

9. Now tighten up the bracket to the engine. I will post the torque setting on an update, sorry I’m so unprepared.
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10. Next tighten up the regulator to the bracket. You know that large nut the holds the regulator itself to the bracket. The washer is waved to act like a lock washer. I really don’t think it needs to be as tight as it was when I tried to get it off…. Don’t twist the regulator because you have that fuel line attached to it. Look at the other side of the engine or previous pictures for proper orientation.

11. Next attach the inlet fuel line (one with hose clamp on it). Tighten hose clamp.
12. Tighten up outlet fuel line to injectors (steel braided line).
13. Connect the vacuum hose to the pressure regulator.
14. Reconnect connector to Idle Air Valve.
15. Make sure all connections are tight and there is no raw fuel ANYWHERE.

16. Reconnect the negative battery terminal.
17. CHECKING FOR LEAKS! Turn the key to the "ON" (not to the Start setting)position. Immediately check your hose connections for fuel leaks (engine off). If leaks are spotted turn off key. Tighten fuel connections as necessary. Repeat this step until leaks are remedied.

18. Now Start the engine, again re-check for leaks. Shut down engine immediately if anything is leaking and repair/tighten as necessary.

19. If no leaks, let engine warm up to temp…. you’re done.
I ran into a problem with the fuel outlet line leaking when the engine was running. You need to be very diligent in checking to make sure you don’t go down in flames. The fuel outlet is the braided steel fuel line to the injectors. I just didn’t have enough torque on it. You can use a clean paper towel to check for leaks all around the fuel regulator. If anything is leaking you’ll see it when you’re rubbing the paper around under the regulator itself or fuel dripping. Better still, rub your finger around the connections and smell for fuel.

I also checked my work every so often when starting the car just to make sure nothing was/is leaking. So far, so good! Guess it’s good to go.

Below is some but not all of the tools I used. You can do the job with just a few wrenches a screw driver and a 13mm socket but this other stuff made things easier.

You can find the regulator almost anywhere. It’s a Bosch part, somewhat common. Many generic parts cross-ref to it, some cheaper than $60.

Job took about 2 hours start to finish.
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Great write up ND. Easy job to do in car by the looks of it. When I do the major on my 348(soon), I will replace them while the engine is out. I dont have any issues, but I also dont have any service records of them ever being replaced either. 15 years old. So I may as well replace them while im there. Cheers again ND, you done well mate.

 

Thanks, but it's not me. Gotta give credit to TMassey.

 

Im sorry. Mr TMassy also. I forgot all about him mentioned at the start of the thread. You both done well with this.
Well, TMassey and you for editing it ND.

 

You can almost read the size of the wrench in your photo - it looks like 13/16". It might be clearer on the original photo since it probably is higher resolution.

Nice write-up!

 

Yep, Tam328 sent me that last night inan email. Dudes star

 

Good write up.

Are early 348's different to late 348's? I have a 1990 car but I don't have a fuel pressure regulator on that bank. Mine is fitted to the other bank but there is no vacuum pipes. Is this right or has mine been changed at some point?

Cheers again for the good write up.

 

I'm kind of new to this 348 thing, but my car looks like it has a dual set up.
One of everything for each bank on the injection stuff.

 

Some early 348's had Motronic 2.5 instead of Motronic 2.7. The 2.5's had only 1 throttle position sensor, and the exhaust ECU's could signal "SLOW DOWN" but couldn't shut off one bank of the engine.

However, they should have had two fuel pumps and two fuel pressure regulators, both of which would have been controlled via a vacuum line.

 

Fuel pressure regulator change update.
this part change has appeared to fix the hot start problem with my 348.

now on to the other annoying things like rattling flywheel, clock flashing,
and other things that are just not right.

 

Ah, another satisfied Brother fresh back from the No Doubt hot-start FPR test!

Life is good.

 

Good to hear brother. Now sort that flywheel crap out and get that bad boy in tip top shape!

 

Correct.........to the tune of 8 cylinders!

 

Nice write up.

 

what is a cold oil pressure for a 348 ts

 

Anyone have a part number for this preferable without the Ferrari tax. Would like to have them on hand before I pull her apart.

Thanks.

Mobilized reply by David

 

Found it.

http://www.ferrarichat.com/forum/showpost.php?p=136095380&postcount=3

 

such a great write up.....thanks a lot!