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Discussion Starter · #1 ·
I am preparing to do fuel pres

I am preparing to do fuel pressure tests. I have the Bosch bar testing gauge.

It is supposed to be connected between the top center FD line and the WUR. The WUR has two fittings: one with two banjo fittings, and one with one banjo fitting. There is a fuel connection between the 2 WURs, through one of the banjo fittings.

I thought of testing one side at a time. Do I need both fuel pump fuses in, due to the connection between the WURs, or can I just test each side, with only the appropriate fuel pump fuse in place?

Discussion Starter · #2 ·
Hi Henry,

you need to disc

Hi Henry,

you need to disconnect the crossover for the tests & you CAN test just one side at a time with only one FP running.

Regards, JRV

Discussion Starter · #5 ·
When one removes the crossover

When one removes the crossover line, one has to get a shorter banjo bolt. The original one is long to accomodate "2" banjo of which is the crossover line. I used a short 14mm head bolt from the TR FD!!!!!!!!!! Well, it worked.

I only did the right side:

Primary Pressure = 5.5 bar

Cold WUR Pressure = 0.6 bar, with electrical connector off.

Warm WUR Pressure = 2.8 bar, after about 5-7 minutes, with the electrical connector attached.

When I applied some vacuum to the base line, the warm WUR pressure rose to 3.5........release of pressure and it fell to 2.8. I didn't measure the vacuum, but more applied and the pressure went beyond 3.5 bar. There is a larger line, which lowers the control pressure when vacuum is applied..........? The larger line comes off the top of the WUR, and the smaller diameter line comes off the base of the WUR........purpose of these lines?

Turning off the pump, the primary pressure dropped to 3.2 bar, and stayed there.......3.1 after 10 minutes.

I had the fuel injection lines disconnected from the fuel injectors and saw no leaks.

Keep in mind that I was not able to start the car from a cold sitting.

BTW: Ambient air temperature is 39 degrees F. I have read that the colder the air, the lower the cold control pressure........thus a reading of 0.6 bar.......does this seem a little low?

Discussion Starter · #6 ·
I am still testing on the righ

I am still testing on the right side of the engine.

I have the tester valve closed, thus registering the 5.5 bar primary pressure. I then connect the saftey switch, and the pressure drops and holds at 3.2 bar........however, after doing this a few times, it seems that half the time, when the switch is connected (fuel pump off), the pressure drops to 1.5 bar.

This would indicate a "sticky" non-return valve on the fuel pump, or the accumulator. It is my understanding that this should NOT cause a cold no-start, however. This may be another problem starting......thoughts?

I will now apply a direct 12V to the cold start injector, to make sure it works.

Discussion Starter · #7 ·
Hi Hank,

.6 is way to low..

Hi Hank,

.6 is way to low...way out of spec. the lowest possible in spec reading would be 2.6-2.8 warming up to 3.2-3.4...

run the test again to make sure you have performed the test correctly and those are 'in fact' the readings.

Like the saying goes, "repeatable, verifiable results.

and yes you must use a shorter fitting...

Discussion Starter · #8 ·
JRV: We where typing together

JRV: We where typing together, while I wrote another post......can you comment on it?

I will repeat the tests, as you say.

Discussion Starter · #9 ·
....hook up gauge and turn on

....hook up gauge and turn on FP...bleed any air in the lines and take the readings...

record Cold, then is nice to start cold although not really neccesary, just to watch for the pressure rise. Once the system pressures are recorded shut of the FP and time the residual pressure readings. If the pressures are to low the system will run abnormally high, abnormally lean...residual prssure fails to hold the car will have hot start issues.

that's about all there is to it...the beauty of a Boxer is you can test the other side also to see if you are getting identical readings.

HTH's..if not then maybe I'm not fully understanding the questions

Regards, JRV

Discussion Starter · #10 ·
Just tested the left side WUR.

Just tested the left side WUR. Fuel pump sounds much louder than the right side! With pump running and valve open, I cracked open the fitting going to the gauge, to make sure fuel would come out, thus insuring no air leaks.

Primary (5.5 bar), cold (0.5 bar) and hot (2.5 bar).......the same.

At primary, when the fuel pump is shut off, the gauge goes to 3.5 bar.......sometimes to 0.9.....just like the right side.

When warm (2.5), and then I shut off the fuel pump, the gauge goes either to 0.9, or 3.6 bar!!!!!!!
I will try this on the right side now.

Discussion Starter · #11 ·
JRV: OK.......I gave it my be

JRV: OK.......I gave it my best shot. I re-tested the left side, and then went back to the right side, and re-tested it.......this time I even used vacuum, per manuals.

Both WURs are acting the same, under all conditions.

Applying vacuum (16" Hg) to the cold pressure raises it from 0.9 to 1.4 bar.

Applying vacuum (16" Hg) to the warm pressure raises it from 2.4 to 3.1 bar.

Residual pressure from the warm WUR, with fuel pump off is either 3.2 or 0.8.......sometimes it goes to one value, and other times, to the other value. What is strange that this is happening to both WURs!!!!!!!! Comment?

Also strange is when I read primary pressure and turn off the fuel pump.....the reading either goes to 3.4 or 0.7, again, on both sides!!!!!!!! Comment?

Why can't comething that is broken just STAY broken!!!!!!!!!!

Discussion Starter · #12 ·

what I don't und


what I don't understand is the low readings...all the other readings seem to be in range....

Discussion Starter · #13 ·
JRV: Thanks for your guidance

JRV: Thanks for your guidance, and support....I don't think I would have tackled this job, without your help.

I got the Bosch # of the WUR from a previous site which you posted them.....thanks.

My plan now is to get a new that I can be sure of these pressures.......the worst, is that I will have a spare.

Is there a site where I can plug in the Bosch #, and get a price. I feel the dealers will be rather high.

Thanks again

Discussion Starter · #16 ·
Just giving some thought to th

Just giving some thought to the situation. Since the "low to high to low, etc." residual pressures, both from primary pressure and from the warm pressure occurred on both sides, I am thinking that either fuel testing gauge is off, or, both accumulators are bad. The latter is unlikely, so I am thinking of the former.

I ordered a new WUR and accumulator. I will test the new WUR, just to see what the readings should be.......then I will keep it as a spare.

Tomorrow I will do a fuel pump volume test. This will measure the amount of fuel coming out in 30 sec from the fuel return line, going to the tank........should be about 850cc. I will report the readings.

I was hoping to take the car to Chicago this weekend, for Easter. Oh well!!!!!! I will visit Continental Motors while there (a Ferrari dealer). I will see what they have. Since I have 2 Ferraris, and BOTH are down just seems appropriate that I get a "third" one........haha.

Discussion Starter · #17 ·
Well, I just completed about E

Well, I just completed about EVERY test related to fuel that there is........and every part associated with the delivery of fuel and air. The final test was fuel volume, which came to 1200cc per side.

I attribute the low readings on the WUR to cold conditions during the test. I even bought a NEW WUR, and the test results where the I have a spare....will place it alongside the spare fuel pumps!

If anyone wants any help with FI on the BBi......just ask!!!!!!!!!!!!

Prior to this, I used my spark tester, and recorded 30KV at the coil output, and 7KV at a plug wire.

Of the three: air, fuel and spark, I have eliminated the air and fuel. The spark is the only thing left. Since it seems I do have spark (I will test it again), if I continue to get spark, then I can only conclude a timing problem. Does this make sense?
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