RobzWorkz #8g: Improving the 328 Fuel System: WUR Rebuild

Greetings FCatters!!

I'm Baaaaack!!! I know it's been awhile since I posted my CIS distributor rebuild, but I've been being consumed as an "on-call engineer" (even though I'm officially a Scientist, I work in an engineering environment).

WRT my fuel system rebuild as awhole, I've had it completed for a few months now and have driven a couple of hundred miles. All is working well. (BTW, my current work is refurbing the ignition from coils to plugs; I'm also replacing the brake light switch---damn those things are CHEAP!).

This thread, RobzWorkz #8g, comprises the rebuilding of the WUR (properly called the Fuel Pressure Regulator since it does more than control warm up pressure). The next thread will describe rebuilding the pressurized flexible fuel lines using SS braid Aeroquip PTFE hoses; the thread afterwards will complete the fuel system rebuild effort with a description of the tests I did. Hopefully Steve or David will chime in to tie up any loose ends...they add well to the peer review here.

The basic functional description of this device can be reviewed in the 328's Owner's manual as well as Charles Probst's well-referenced book "How to Understand, Service and Modify Bosch Fuel Injection & Engine Management." However, some details are not present in any of these periodicals, namely the reason for having 2 resistor-varied bimetal strips inside the assembly (at least they both look like bi-metal strips, certainly the bottom one is since it is mounted to the base so as to serve to control engine-warmed fuel pressure). No control circuit diagram was available for this. Since, there is only one electronic line presented to the device, and I could only discern one path in the 328 electronic diagrams, I expect that both these strips work together to balance the controled signal in a mechanical way. I'll let Steve chime in if he's interested. Anyway, the rebuild can still continue as long as the configuration doesn't change and the electronic parts don't look useless (if they do look too bad to reuse, then buy a new WUR or send to Larry Fletcher so he can exchange it for you).



Now, to rebuilding the WUR:

First, I must give much credit to geert Jan Schreurs (www.ferrari400parts.com) for designing and making the rebuild kits available; he has also published some (more general) rebuild guides for all CIS components). Additionally, geert Jan has provided an additional component for WUR's that allow for changing cold system pressure in both directions without dissassembling the WUR to push out the adjustment bar; baseline adjustment was made by tapping the bar (only) inward to finally adjust cold pressure; the new bar provides the ability to pull out the bar by cranking a nut; this allows for DIY re-adjustment.


Remove the WUR:
Disassembly is straight forward, however, be sure to keep everything acounted for and take pictures as a reference. I am disassembling the 328 US Version WUR from 1986. There may be variants...therefore, making a record is heavily advised. Also, before disassembly, contact geert Jan to be sure a proper kit is available.

Pic 1 below shows the WUR removed from the engine (see RobzWorkz #8a for disassembly).
The remaining pics show various views of the WUR as removed. At this point, you can remove the bracket that attaches it to the engine; I needed a hex wrench to remove mine.

At this point, clean the WUR outside very well.
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The "first" disassembly step involves dividing the WUR body, removal of small parts and removal of electronics. The "second" disassembly step included removing the brass control rod and the upper small diaphragm assembly.


Again, disassembly is fairly straight forward. However, a few caveats are in order:

1. keep track of everything;
2. take pictures for reference;
3. there are small parts, especially the control rods (mine has 2, one is "by itself" and looks like a simple pin and the other is attached to a base; both work with the diaphram spring);
4. remove the U-clip holding the electrical connector before dividing the WUR body; this will prevent undesired stretching of the wiring;
5. did I mention to keep track of everything.

The process:
1. Remove the two fuel lines from the top of the WUR by disassembling the banjo fittings.
2. Using a screwdriver, remove the U-clip from the electrical connector.
3. Place the WUR (for mine, upside-down) in a "cushioned" vise (cushioned with duct tape is fine); using a LARGE flat blade screwdriver (assuming you have flat blade screws, of course), crack loose the 4 body bolts; these are not very strong and old worn bolts may shear in half; if they do shear in half, they will separate when the body is divided.
4. Separate the body with a wide flat-blade screwdriver, keeping track of the small parts; there will be a gasket between the body halves; look for the spring and control rods (recall, in mine, one rod was loose, the other had a base); if possible, note (take a picture) the orientation of the rods and spring for reference during rebuild work; do not be afraid if these parts become disorganized; there is a logical means for identifying their orientation for reassembly; NOTE: the electrical wiring, brass control rod and bi-metal strips are mounted to the body halves, so you can't fully-separate them untill the lower bolt is removed to free the lower bi-metal strip.
5. Using a 10mm wrench, remove the lower bolt that retains the lower bi-metal strip; remove the lower strip from under the lower diaphragm top plate; now the two halves are now fully-separated.
6. Using the wrench, remove the lower nut on bottom of the brass control rod and remove the electronics; keep the electrinics in proper order by arranging onto something straight (I used a Q-tip).
7. Both body halves should be empty of loose items; you will see the brass control rod and the upper diaphram plate assembly (4 small screws holding in place...mine were horrid-looking with rust) on the upper half and the lower, larger diahragm (made with corrugated sheet metal located under the divider plate (this is the surface onto which the spring is located) on the lower body half.

See pics below for visuals of this procedure; the next post will describe internal cleaning and then removal of the control rod and upper diaphragm assembly.
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Now clean both body halves to remove rust and deposits. I used a Dremel wire wheel on the surfaces and used an XACTO knife to score off the rust from other areas. Use the XACTO knife to clean the 4 screws retaining the upper diaphragm assembly including the screwdriver slots.

I recommend spraying some PB Blaster into the screw holes from inside and outside and letting sit. You definitely do not want to shear these during removal.

Loosen the 4 screws retaining the upper diaphragm, noting all parts. There are 8 total parts to keep track of here:
1. the assembly backing plate (thick plate);
2. 4 small screws;
3. a small plate residing in the center of large plate that is controlled by the small pin rod/spring assembly and the lower diaphragm in the lower body;
4. the upper diaphragm (thin metal plate), and;
5. an o-ring.

FYI, the rebuild kit only provides replacements for the 4 small screws, the o-ring and the thin sheet diaphragm.

Clean the two plates (large and small), making sure the small plate lies evenly and loosely within the large plate (no ticks, etc). I used wipes and a soft Dremel wheel (brass is good). The important thing to remember is that this small plate is the interface between pressure applied by the lower diaphragm/spring/rod(s) and the thin metal upper diaphragm. It needs to be free to move.

Everything else (surfaces and the o-ring slots) should clean well with a mild solvent and Q-tips.

Finally, remove the brass control rod:
1. NOTE POSITION OF THE ROD FROM ABOVE (this will be the approximate position to reinstall later).
2. Apply PB Blaster from inside the upper body and let sit.
3. Tap the rod from above to remove: place upper body on table with room for the rod to move and tap with a rod and small hammer;
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The first 2 pics below show the rebuild kit and the new upper diaphragm. The 3rd pic shows a comparison of the new control rod with the old (actually they are not brass but steel...I just thought they were brass...my bad); as can be seen the new rod has threads on the top; these threads allow for pulling the rod up from outside the WUR while in the car to adjust cold control pressure. Note, the upper shoulder (below the upper threads) of the new rod corresponds to the top of the old; it is with this shoulder that the position will be started as referenced by the top of the old rod (that's why you took a pic of the position, right?).


Install the upper diaphragm assembly:
1. insert new o-ring into groove in upper body;
2. insert small plate properly into large plate (recall, this plate is pressed upon by the small rod/spring so the small cup part is positioned to the rod while the flat to the diaphragm);
3. place new thin metal diaphragm into position onto large plate, aligning the 4 holes (note, my replacement had an extra hole that seems to be unused with my WUR...no additional holes were present with which to align the 5th hole);
4. install the 4 screws tightly (by hand with small flat blade screwdriver); I used a drop of Indian Head to cement the threads here.

Also, I used a toothpick to align the screw holes.


Install new control rod into upper body:
1. to do this, first clean the inner cylinder surface until smooth...mine was smooth enough to clean with a Q-tip, however, polishing with 1000 grit paper rolled roughside out can help.
2. I "lubed" the new rod with dielectric grase (basically silicone) to help it move and seal.
3. I used a nut and three larger diameter copper washers to pull the rod into position (the washers comprised the back seat for pulling the rod through).
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Clean and ensure whole and functional the electrical piece (mine consisting of 2 resistor controlled bi-metal strips, a retainer, wiring and connectors). If necessary, resoldering can be completed, but only if the resistors are intact (again, if this is non-functional, get a new WUR). Don't forget the arrangement of the parts.

Install electrics as follows:

1. place a new gasket (from the rebuild kit) onto the externel electrical connector (remove old one first if not done...).

2. install the lower bi-metal strip onto the lower body half (perhaps "into" is a better word since it inserts into the area enclosed over the lower diaphragm...however, it is bolted onto the body half); position the lower strip so its U-shaped end is aligned with the pin access hole over the reinforced part of the lower (corrugated) diaphragm; tighten into place (modest tightness...you can use threadlock if desired).

3. slide upper bi-metal strip and retainer onto the control rod in the upper body while aligning the external connector with its access hole; be sure to put in proper order; when fully inserted, place some Indian Head varnish on the control rod threads and install the nut; align the upper bi-metal strip's hole end with the cup of the small plate in the upper diaphragm assembly; tighten the nut (mild tightness).

4. install U-clamp onto external electrical connector.

Pics below:
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Final assembly involves placing the body gasket into the upper body groove, using sticky grease to place/stick the spring and rods in proper position and bolting the body halves back together.

It's really that easy, however, be sure to position the spring and pins properly and be sure they seat into proper positions:

1. upper pin into cup in upper plate of upper diaphragm assembly;
2. pin with base so it will strike the lower diaphragm on its reinforced section (through the hole in the divider in lower body onto corrugated diaphragm); this base rests on the curved bottom of the upper bi-metal strip as shown in the pic;
3. spring into indent on divider plate of lower body (I positioned the spring inside the upper body and aligned when assembling the halves);

This is why sticky grease is used.

After assembling the body halves (mild hand tightness to seat the gasket), you can install the engine mount bracket.

All done! This can now be installed onto the engine. Be sure to use new copper washers when installing the flexible fuel lines.
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Thanks, Andy!

Intake vacuum is also used with this one as well. You will see this in my testing thread.

 

David, if you are willing, please post a copy of this WSM description.

It is true that the vacuum sense is located on the ATM side of the butterfly, making it suited for barometric compensation. However, I could not discern if there was an aneroid chamber in this WUR (the aneroid chamber is described in Probst and used for barometric altitude compensation). Also, I saw no indication of vacuum effecs on the WUR in the available Ferrari 328 technical literature.

Probst indicated that a vacuum tap could be used to provide enrichment when opening the throttle from part load to full load (both conditions where engine vacuum would be presented to WUR model 132 as attached). I verified this when I checked that adding vacuum increased control pressure, causing a leaning condition; the converse (i.e., enrichment) would occur when the engine goes from part to full load. BTW, I only checked for vacuum change at cold temp; since there was no spec associated with engine vacuum in the 328 Tech spec manual, it was only a simple check (per Probst). All other customary specs were present in the manual.

For details, see Probst (5: p21 and 6: pp16-19).

 

Andy, thanks for the check. There certainly are generalizations in Probst. That is why I would like to have something Ferrari 328 specifically described. The hole in the bottom looked sealed (I didn't pressure test or leak test). It could be used for compensation if open to ATM (probably for a different car and/or altitude). It looks like an "available tap."

The vacuum tap is certainly for vacuum, albeit pre-throttle. I still believe it's for enrichment going from normal load to full load. BTW, some pics only had one large port (see Fig 5-2 in Probst; Fig 5-3 looks more like the 132 however, there isn't a side port for anything on the 132; I would think the sealed bottom port on the 132 could be made available for high altitude compensation). If the top port were only to vent to ATM, then why would there be a hose to the TB?

Thanks guys.

Some things are just PFM (Pure ****ing Magic), especially if without documentation from the Max Planck Institute.

 

Great catch Lonnie!

The rebuild kit came with a replacement screen. Since mine wasn't clogged and it cleaned out well, I did not replace it. I forgot to mention this. Carb cleaner works well here; use the tiny red plastic hose/pipe and wear safety goggles; it's best to clean out from inside spraying through the little holes there, you should see flow when cleared (see pic 13 on the same post to see the 2 holes).

 

That's a good idea. I've already tested and adjusted the system based on 328 tech specs; I did a "free check" of cold pressure increase with vacuum applied. When I get the time, I will consider a special test, which would show vacuum cold and warm and associated control pressure variations. This could be considered dynamic testing. I'll consider a video of this. When done, I will include in my testing thread.

BTW, my understanding is that "heavy load" is when the engine has significant resistance to its speeding up, like when the wheels are on the ground and speed is increasing. This, of course, would be a different test and would not entail attaching the CIS tester (not safe to do when driving...can't be monitored for safety). The vacuum line would be extended to a guage in the cockpit. Am I correct here, Steve? The above test (previous paragragh)would identify the relationship of engine vacuum to control pressure, while this test would identify the vacuum present during normal operation.

 

I had to do more research on aneroid chambers. It appears that the corrugated lower diaphragm may be the actual aneroid chamber. It's hard to tell since Probst discusses multi-diaphragm systems and the lower diaphragm looked flat to me (like an additional diaphram vice a chamber as in an aneroid barameter).

I'm pretty sure the small port seen from the bottom is the tap port for the bolt retaining the lower bi-metal strip. It looked sealed.

If this is the case, the aneroid ATM pressure access would be through the port on top. This becomes more interesting since this port is attached to the intake TB and not simply left open to ATM. There still could be a relationship between engine vacuum and the barometric compensation of CIS pressure. This would imply more than simple altitude (or barometric) compensation.

 

I agree too. This brings things into perspective. Cool air could cause undesired change to the WUR operation. Steve, I will consider the "T-fitting" test later (when I get a Round Tuit...only got square ones now)

(Also, I do think "swag" is an interesting synonym for "algorithm" )