350se dies when warm

[milo]

Hi all
Been messing with this 350 for far too long, the question is does all primary fuel regulators have a removable piston?
This is a cast iron FD which has been rebuilt but when attempting to fit the new needle with the 3 small rubber o rings it will not go in. The original didn't have any rubber parts on the nose of the needle but i've been re assured by the supplier the new one is correct.
I have tried many times using system fuel pressure and air line pressure to remove any other moving parts in the FP Reg orifice but can't see any .
Looking into the port there appears to be a brass fitting with a hole that allows the rubberless needle to go in but I would really have to push with more force than I'm happy with.
Any info would be appreciated, ive been on this problem since forever.
PS car starts and runs but as it warms the idle falls till eventually stalling.

[Randys01]

Is this a K or D jetronic?

[milo]

Sorry , K jet its a 1980 model

[milo]

No one any info on the primary fuel pressure regulator then? Is there two types of design, one with rubber parts on the needle and one without?
I don't mind educated guesses, anything is better than nowt.
cheers.

[daantjie]

You will need a fuel pressure test gauge to be plumbed in between the fuel distributor and warm up regulator to start with.

[Randys01]

 1. Not sure why you have homed in on the FPRV as the source of your problems but whilst there are 3 variants apparently, a late model cast iron FD suggests possible later type.?
2. The function of this valve does not alter whether the engine is hot or cold.  It is used to set the system pressure using shims and there are at least 2 rubber O rings. Normal is 5.5 Bar.
3 As Daniel said you will need a fuel pressure Test kit to diagnose this. 
4 After fooling around with K jetronic for 10 years or so I can tell you this.  It is nigh impossible to walk up to  a faulty vehicle and point at some part of the K jetronic and say...mmm  yes yes..I reckon its the wigwam for a goose's bridle.
You have obviously spent too much time mucking around with this and with out the test kit you are just shootin' in the dark. Even with the Kit a 100 adventures lie ahead.

This is a system that needs sytematic diagnosis.   A must be correct before moving to B before C.
That said, the fact your engine fades when its hot suggests a double check of the cold start air flow thermostat and idle air circuit is worth eliminating.

BTW...removal and refit of the FPRV needs tlc.  it's a proper mongrel when the FD is on the car. use a torch and a mirror to examine the bore of the FD and make sure there is not an old O ring sitting down on the seat.

[revilla]

True.

But in my cases hot-start problems were always connected to one of these three areas, but I agree it could be 1000 other k-jet adjustments.
Fuel accumulator with broken diaphragm thus not holding pressure
Cold Start Valve leaking. It suppose to open momentarily only when cold, but if the little injector continues to flow after shutdown your engine will be too rich to re-start quickly once hot. This apply to your other 8 injectors too btw.
You might have an air leak too, the engine starts cold no problem because the wur enriches the mix so excess air doesn't hurt, but when hot your engine has trouble dealing with too much air (too lean) thus your troubles on hot-starts.
As mentioned by Randy, I neither had a bad system pressure or main pressure regulator that would cause hot-start issues.  Only one time I found a partially broken external (there's in internal too) oring that was causing the piston not to freely move, but no apparent effect on performance.

But to answer your question, I have only seen pressure regulators without a rubber stop at the tip to interface with the inside of the piston. I have only seen the needle that is metal with some sort if black coating, to avoid metal to metal contact I guess. I can send you a picture later if you wish.
When dealing with k-jet investing on a pressure gage (even a very basic simple one like mine) is a good idea.
Hope it helps 

[revilla]

After re-reading your original post I can confirm the piston (no rubber, no oring) is the last part (first part you insert into the fd) then it's actuated directly by the needle on which you have already inserted the shims and the main spring.
There's an internal oring that which you can access by the allen screw in the middle of the 16mm main body. I have never messed with it and my cars start quick cold or hot.
I would install it as described and measure your system pressure (spec is 5.2-5.8 bar).

According to your description, you might rather have a WUR which is out of spec.

Your engine starts fine in a condition when the WUR keeps the mixture rich. Then it slowly (first warmed up by the 30ohms resistor inside and later by the block temperature) leans out the mixture which causes your engine to die.
To test this hypothesis I would this little easy test.
Remove the mixture screw at the top of the FD. Insert a 3mm allen key until you reach the adjustment screw inside. Careful not to push too hard. Remove the 3mm key but keep it handy. Cover the hole with a temporary tissue, careful it doesn't get sucked in. I use a little plastic cap that came with my injectors that fits perfectly.
Start your engine. Let it warm up to the point when idle starts to deteriorate. Insert the 3mm key delicately not forcing it down. Turn it clockwise (you're essentially letting less air in the mixture) but with very little moves of about 5deg max.
If your engine regain a decent idle then your WUR is overcompensating to the lean side. It's needs to be recalibrated which is easy, we can help you with that later. But let's first test this hypothesis.
All this would be much easier (and scientific too) with a pressure gage because it would tell us exactly what is the WUR doing inside through the reading of the control pressure all along the cold-hot cycle which is priceless to determine corrective actions.
Please let us know.

[milo]

Thanks very much for all your thoughtful responses, I really thought I was not pushing a signal there.
OK I have a fuel pressure gauge attached indeed it has been attached for maybe a year now, the cold pressure values are within spec as are the hot, I have modified the WUR to allow adjustment of the fuel pressure as the car is running.
I understand as the WUR mech. operates it increases fuel pressure to the FD causing the mixture to lean out to hot running condition, this I have,also I use a glass spark plug to give a visual on the burning gasses
I have removed the aux air valve several times to test and double test for correct operation , it leaves a small sliver of air gap when fully warm which I understand is correct.
Here is a list of some other works.
Both heads removed, new valve guides and valves on the dicky cylinders.
New injectors and seats tested for leaks.
Timing chain uppers replaced with cam timing almost perfect.
FD rebuilt twice using all new parts and taking care to be certain the slits within the instrument were completely clean.
I couldn't convince myself I had done this the first time hence the second rebuild.
Fuel tank removed and cleaned twice , I can blow down fuel return line into tank with my dweebly lung power so im happy that's OK.
There maybe a few things im forgetting but what im trying to convey is ive been as thorough as I can and put a fair bit of work into this thing so when I ordered the new primary pressure valve complete with new rubber bits on the tip I really thought it could be a fix, it just will not go into the hole easily and I don't want to force it.
Looking at google images the PP Reg seems not to have the rubber bits on the when installed with the piston assembly,
my PP Reg listed for the350 se does.
By the way I use various inflammable sprays to check for any air /vacuum leaks all over the inlet manifold area and anywhere else.
Since doing all this work the car starts on a high idle , higher than I would like then as it warms it settles to a good idle then after about more than five minutes {never timed it} it just gets slower and dies, at this point im furiously adjusting the mixture in small increments , watching the fuel pressure doesn't get to high and purposely lowering slightly to allow for inaccuracies in my gauge.
PS I don't have a fuel accumulator installed.

[revilla]

Excellent
With the symptoms you described, the only 2 parts I can think of that would affect idle from cold to warm cycle is the WUR and the AAV. Others can add please.
That said, what is your needle doing when the idle stars to deteriorate? Does it vibrate? Or is it steady? At what value does the idle deterioration starts? At value does it die? When is about to die does response to acceleration?In other words, can you maintain high revs manually to avoid it dies? Or it will die anyway? What is the ambient temp when you last run the test? In fact, can you share CP cold, CP warm and System Pressure values?

If you get the correct SP, your Pressure reg, your pump and your lines are fine. To answer your concern, the P reg goes in by hand about 2 turns without effort. Then there's some resistance to be turned for about 3-4 turns. Basically you're "fighting" the spring to be compressed and push the piston all the way in. The last few turns you can't do it by hand, you need a wrench.  Yes, it's a bit hard I would say.  Impossible by hand. There's no rubber piece in-between the needle and the inside of the piston, neither on the tip of the piston. Maybe you can send a picture please.  I have both type of FD in 2 separate cars and the piston differs slightly at the tip (1 or 2 mm longer tip). But I have swapped to test the difference and literally no changes in SP or CP whatsoever or performance.  I don't believe there's a difference in P regs by model (e.g. 350SE) but rather by FD type, there are 2 to my knowledge.

From your list, have you checked that your WUR is getting the correct amount of vacuum? If not, it will do what you're describing. Have you opened the 'valve' part of your WUR? Sorry I don't recall seeing that on your list.  Is it not clogged? There's a small filter in there (not always, depends on the WUR). Plus the little plated disc that is essentially your pressure reg valve? Is it clean? Free to move/flex? How about the spring(s)?

I ask all this so you can help us help you

I'm sure you have done all/most of that, let us know please.

 

[milo]

HI Rab
Don't have the quick reply thing going on so cant see your questions for reference.
Fuel pressure does not fluctuate at any point but I didn't know the vacuum side of the WUR did anything so havnt paid it much attention all I can say on that score is the vacuum hose is connected , all my attention has been on the fuel side of it.
I will have a thourough look at the vacuum side thanks.
Re the Pressure reg I really need to post a pic or two to allow clarification , my hopes were the fuel pressure dropped jus for a split second t as I revved the engine and it dropped back to idle and yes that's when it happens, I didn't make that clear, the engine revs like a smooth thing in an impressive way right up to the point where its fully warm then a good stab of throttle will cause it to die, bummer.
I will re visit yours and others helpful responses and post back.
Thanks guys.
is uploading pics tricky?

[daantjie]

AAV must close COMPLETELY at operating temp.  If it leaves a gap when fully hot it is faulty.

[milo]

What not even a tiny sliver?

[revilla]

What not even a tiny sliver?

That's not your issue then. A tiny sliver will slightly increase your rpms, but won't trigger the failure mode you described.

Cheers

R

[revilla]

is uploading pics tricky?

Not so tricky, as long as you compress them not to exceed the limits. If you do the system will give you an error message explaining.  Use the 'Attach' button and not the picture icon.

Cheers

R