Cleaning the filter of the 348 / T fuel pump assembly

Pay-back time for the F-chatters !

I have learned a lot about my car and it’s quirks from all of your experiences and answers to my questions, so now finally I might have something uncommented before that benefits the community.

In an earlier thread I was wondering why my car lost power on acceleration once getting down to approximately half a load of fuel.
With gratitude to Ernie’s excellent tutorial about how to disassemble a 348 fuel pump I was encouraged to take them out to replace those rubbers that had disintegrated on his car leaving plenty of debris in the filter.
My assumption was that due to cracked rubbers my pumps might be moving freely in their cases and hence allowing for air to be sucked rather than fuel once the level was low enough for the pump to be no longer fully submerged.

I was only partly right……

References:
My initial symptoms: Seems like Pitlane limiter | FerrariChat
Ernie’s tutorial: 348 fuel pump rebuild | FerrariChat
Pump rubbers found at:
Autoricambi d'Epoca SRL / Old-Timer Parts
Via Maget, 2/A - Fraz. Ragoli
38095 TRE VILLE (TN) - Italy
Phone: 0039 0465-322159
Whatsapp: 0039 379 1841512
Website: www.autoepoca.it
Email: [email protected]
Regarding the purchase at Autoepoca.it (no affiliation): Those rubbers may have been available at other’s too, but they had them in immediate stock at my side of the world and reasonably priced. Friendly attention and adequate shipping, however they could have done better upselling had they known the assembly of the pump itself (see my comments about the wire cowlings later on).

I must admit I got carried away writing down my experiences, so in case you are not in for a lot of text, just scroll down to the last picture and read the outcome – no hard feelings.

 

1. Unveiling the pump

Ernie’s tutorial has been very helpful is detailed and undoubtedly the best way to take the whole thing fully apart.
With absolutely no disrespect to his methods I took some shortcuts that may also derive of:
- Having a Mondial T vs. a 348
- Not dropping the fuel tank
- Not wanting to unbolt anything but the necessary (“never alter a running system”)
- Not needing to replace those rubbers after all
- A lesson learned working the first pump

First you will need to remove the bottom plate that is just up front of the engine. Once removed you have clear sight of your two fuel pumps.
Albeit the car was on a lift, I had to jack it up a bit further in order to be able to hold a funnel under the drain plug.
I started on the starboard pump only for the better accessibility of the drain plug.

Image Unavailable, Please Login

Once drained, the pump drops after having unbolted the 8 nuts (wrench size 10).

Image Unavailable, Please Login

First findings: - The rubber vibration dampeners actually seemed to be in a very good condition.
- No sign of wire cowlings anywhere

 

2. Dismanteling the pump as far as needed for inspection

After having lifted the cup from the bottom plate following Ernie’s steps, I also found barely any debris that would indicate rubbers to have disintegrated.
Image Unavailable, Please Login

Lesson learned: When taking step 6 or 7 of Ernie’s tutorial (photo 14), squeezing the plastic clips on the nozzles with pliers, I noticed a slight cracking noise when it finally came off. Fortunately it did not snap, but yes, it had a crack in that suspending ring so I decided to try to work on without having to
unfasten the other hose’s clip.
After all I did not have replacements for those O-rings at hand and thus no necessity to remove the hoses other than for ease of dismantling other parts.

Wondering how to fulfill the step where Ernie used the long screwdriver through 3 bottom holes (his pictures 23-26) that in my case were filled with a 3-star rubber mat, I felt that the pump was too lose in the cup than to be bolted or clipped.
Hence I gently pulled whilst wiggling the cup and it perfectly slipped out.

Uuuughhh !!!! What is that ???
Image Unavailable, Please Login

Now unless “The Blob” had a wank into my reservoir somewhen the last 31 years, I have no clue what this grey slime, clogging the filter’s mesh, is supposed to be.
Maybe a chemical reaction ? But I for sure never filled up with E10 gas and even try to avoid E5.
Later on I was consulted it was “gum” and it seems to be part of our gasoline……… WHAT ??

I have to pay $$$ at the pump to get rubbery gue into my system ???

What if this gets into the injectors ??? Now this called for some thorough cleaning.

 

3. Suspecting the cause of my initial problem

The filter cup can be separated very easy by undoing 6 small X-head screws. Fortunately it seems to have done it’s job, because my pump looks rather clean.
Image Unavailable, Please Login

At this point I am getting to suspect the cause of my initial symptoms:
As the mesh is almost completely “gummed – up”, how would sufficient fuel be able to be sucked in by the pump ?
Well, you may have noticed this small, black, vertical straw sticking out right next to the pump. (Best viewed in a photo further down where the other pump is dropped) This feeds into a tiny (1,5mm) hole in the rubber dampener allowing to BYPASS the filter’s mesh.

So probably my pump was feeding itself sufficiently through this bypass, until such time that the level of combustible liquid would drop below this snorkel’s inlet..
That would explain why I never felt any lack in power with a full tank, but especially when trying to accelerate once levels got half way down.

I was tempted to block this bypass completely in order to keep any debris or “gum” out of my pump, but Bosch (and/or Ferrari) must have chosen this set-up with a purpose so I decided to leave it as it was.

 

5. Cleaning the filter

Happy about probably having found the cause of my initial acceleration problem, yet shocked with what I had found being the cause, it is now time to clean this mess up.
A quick look by mirror and/or camara into the tank itself assured me I would not have to drop it. Great – now for the filter:

After having wiped and peeled off the worst contaminations, it was obvious that the pores of the mesh would benefit of some more profound attention.

First thought: Magic spray for all oil stains - Brake cleaner ! Let’s give it a good spray….. Nope.

Water then ? Nope. In fact, the filter cup fills up like a glass of water and overflows, clearly indicating insufficient flow through the mesh.

I took it to a trusted mechanic who also fetched his can of Brake cleaner only to be disappointed. He then suggested to soak it a night in dishwashing detergent. So I did. Actually 48h just to be sure….
When brushing it with an old toothbrush, the foam got nicely black, so something must have been washed out, but the improvement was insufficient. The cup still filled up to overflow when held under the tap, albeit slower.


OK, let’s see what we have in the basement:
- Cleaning gas (Naphtene 100/140) the stuff the dry-cleaner uses to get stains out of your garment
- Paint Thinner (Terpentine)
- K&N Filter cleaner

Given the filter’s mesh is divided into 4 sections, here are the side-by-side experiences:
(bare in mind the whole thing was already soaked two days in the detergent and brushed once)

1. Another thorough brushing with dishwashing detergent
OK, it got better, but the majority of the pores still seemed clogged
Image Unavailable, Please Login

2. Naphtene 100/140
Smelt like at the dry-cleaner’s, no foam when brushing, and also the result was mediocre
Image Unavailable, Please Login

3. Paint thinner / Terpentine
The toothbrush got black so it must have washed something out, result seemed promising
Image Unavailable, Please Login

4. K&N Airfilter cleaner
Foaming when brushed and black it was, but I was still not satisfied with the result
Image Unavailable, Please Login

 

6. Next thoughts.

As I am not a chemist, I could only reason the following: As paint, especially latex based paint gets sort of rubbery when drying, the paint thinner must have some effect in softening the components.
And when you want to clean your brushes, you would probably leave them in for a night.
So I decided to soak the filter cup in paint thinner for a night.

Brushing next morning in a kitchen full of fumes that had evaporated through the night made the toothbrush disintegrate completely, which makes you wonder…..
Image Unavailable, Please Login

Fortunately the filter cup withheld that bath but the result on the mesh again was not good enough.

Given the experience with the paint thinner (including my wife’s comments on the smell in the house) I was not going to do the same with Naphtene, and went for the last option: A night in the K&N air filter cleaner

Some good brushings next day and the foam got whiter and whiter indicating the cycle’s end.
Ok ok, there are still some stains, but this should do.
Image Unavailable, Please Login

More important: when held under a tap, the water just went through the pores like a knife through butter… ! …. imagine Bricktop saying that ; )

 

Thoughts about the wire cowlings....

Reassembly speaks for itself. God bless the plastic clip of the pump tube that started cracking on dismantling did not part when pushing it back on.

I bought 4 rubber wire cowlings as Ernie replaced them in his tread, but mind you my pump had none in place. In fact, NONE of the wire connection points inside the tank were covered by any cowlings, making me wonder the following:
- are they essential ? after all my car ran fine without them. Or are these swords of Democles if ever one would bridge a spark ??? Kabooom ?
- but then, why would they be only placed on the connectors on top of the pump and not at the 3 other connection points of the wires down at the pump’s base plate ?
Autoepoca.it could have sold me 6 more cowlings to cover them all up and feel safer that way. ……. next time.

When bolting back the drain plug, I was afraid the thin O-ring might warp between the dry surfaces of pump plate and drain plug, so I lubricated it a bit with grease before fastening.

 

7. Second pump

Car was lowered on starboard to be lifted on port side for the next pump. This time I did not even bother draining as whatever amount of fuel might still have been in the tank must have flown to the lower side of the car, immediately allowing to check if that side was “water”proof again. It was.

So with only the 8 bolts unfastened the pump dropped and again the rubber looked fine. No wire cowlings either on this pump.
Image Unavailable, Please Login
On this photo you can see that BYPASS – straw sticking out to the bottom right (as the pump is on it’s side)

Loosening the two nuts on the bottom plate that hold the metal retainers was sufficient to slide them out of the way and separate the cup and pump.

Aaargh !!! that filter looked even worse !
Image Unavailable, Please Login

Blobby !!! *@*#!

 

8. What you've all been waiting for:

6 X-head screws later it was off for the cleaning procedure, only that now I decided to soak it a night in a bath of K&N air filter cleaner.

Scrubby Scrubby with the toothbrush (repeated until the foam got white-isch) produced a similar result as with the first filter, so there you go: K&N Air Filter Cleaner does the job.

This is where one of my kids came in and wondered about the material of the filter. I gave it to him to get a feeling, and noticed that the spots where he rubbed it between his finger tips became virtually stainless…… hum ?

Quick dip into the K&N stuff again and I massaged it all around.

Tadaaaaaa !!!!
Image Unavailable, Please Login

Now I do not know if in the end it was the K&N ingredients or the massage of the mesh, but you may note this one:

Gummed up filters of your fuel pumps get to shine like new by soaking them in a bath of K&N Air Filter Cleaner for a night, brushing them out until the foam gets to be white and then massage the mesh between your finger tips. (one inside one outside)

Happy cleaning !!! (and NO, I am not a sales representative of K&N)

Mondi Cab