Follow on from Bradscat post (new thread started)

I recently changed the two FPR (Fuel Pressure Regulator) valves on my 1983 HE.

I am having starting issues, I have to prime the pump 5 or 6 times to get it to start, you could hear the fuel rushing through the pipes when the bonnet was up.

Also, when it was switched off, you could hear the fuel run back into the tank.

Now then, since changing both FPR valves I don't hear the fuel running back into the tank, but it still needs the ignition switched on and off 5 or 6 times before it starts.

I was told by McMillan Jaguar in Motherwell to check the vacuum hose at the ECU, there is no vacuum and it is split by a T-Piece (see pic)

When I blow down the pipe there is no back pressure, due to the T-Piece I am thinking. (Explained in Bradscat post by Greg In France)



[Greg: XJS V12 1985
The T piece sends vac to the Rochester valve, which is a small black round flatish thing hidden up the side of the tank. This valve vents the tank to atmosphere, but needs a slight vacuum to open it. The idea being that when the car is stationary the tank cannot vent, but when it is running it can. Your Rochester valve may have failed; but as long as it fails open, it does not matter! On UK models, like mine, with no vapour cannister recovery system, this valve was fitted roughly where part number 28 is arrowed in this diagram in the link:
https://parts.jaguarlandroverclassic.../brand/jaguar/
In USA cars, the Rochester valve was fitted in th engine bay as part of the vapour recovery pipework, but it has the same function; to seal the tank when the engine is not running, number 8 in this diagram in this link:
https://parts.jaguarlandroverclassic.../brand/jaguar/

Block off the T arm that does NOT go to the ECU, and then test for vacuum as below.
The vac source comes from the balance bar across the back of the engine that links the two manifolds. Sucking on the ECU end will show some resistance, but you will be sucking some air through the butterflies, remember. If there is a bit of vacuum doing this, then the vac line is probably OK. If not, then this has to be investigated further, so post again.]

I commented that should I not blow down the hose seeing as its a vacuum.

Cheers.

Graeme

 

Coupla issues there.

The fuel priming with NEW FPR's every time, is NOT right.
You have bleed off, and that may be:

Injectors
Cold Start Injectors, IF fitted.
Duff FPR's, mainly the B Bank unit as it is the REAL pressure regulator, the A Bank is a damper and can be eliminated.

That Vac hose, NOT good. Replace it. The ECU will OVER fuel with a split like that, because the ECU is simple in its thought processing,
Less Vac = More Fuel, More Vac = Less Fuel. A split like taht would be very lucky to even start it.

We did not have that "T" and valve Greg so clearly explained, so I will stay out of any discussions on that.

 

Update. I found the Rochester valve, it is attached to nothing, it was laying there attached to the hose, but then attached to thin air.

I blew down and sucked on the hose after crimping the Rochester side, air flows quite freely, not sure how much pressure there should be when blowing or sucking (cough cough).

I have a friend that has a ramp, I will get it onto it start of next week, see where is goes to and if its split..

 

I am thinking of sorting out the t piece and replacing it with a joining piece and just connect it to the ECU, the Rochester valve is doing nothing anyway.

Gee.

 

OK, this sort was quicker.
Update to the Update,
Crimped it, two turns of the key to prime it, just incase...and it started up first time.
I will give it another go, no extra priming this time.
Running slightly rough, but i am thinking it will need a run to sort out the old settings of the ecu.
Will post back later.
Rona's XE going into the dealership today to sort out her Diamond Cut Alloys that are all corroded. Ridiculous!

 

Goodo, simple cars these V12's.

NO amount of running will do anything to that ECU, it is NOT a learning ECU at all.

A good long hard run will clean out years of gunk, then the "tune up" can begin.

Well done so far and good luck.

 

Took the car for a blast and put some go go juice into her, the full bhuna 99 octane, it doesn't like the 95.

Starts on the key now first time, a bit slow in catching but a dab on the throttle helps it.

It will be getting plenty of runs.

I sorted the adjustable suspension, much better now, it was far too hard, cars rear end was bouncing in a firm way, much smoother ride now.

Gee.

 

Hi all, I thought I would give you an update on the starting issues with my 83 HE.

It all returned to the start (Bad) after a day, I could not understand as to why. It was worse to get started

I had a day/night away from it, work took care of that.

Last night while driving my truck back home from Birmingham, the UK one, I was exercising the white cells as to why. (it helps with a 15 hour shift).

The only thought was a bad earth that I had seen, well, a broken earth.

My experiences of earths are different from XJS earths, on the XJS it just seems to slow things down, on my Clio Cup, it stops things working all together.

That's what happened with mine, its slowed everything down. The alt wasn't charging the battery, the battery didn't have the amps to turn the V12 or even prime enough fuel.

I fixed the earth, hey presto, amps up, turns more freely and the fuel pump pumps like a younger version.

I won't hold my breath until a week has passed and then I wont hold my breath.

Cheers.

Gee.