300-24, spark plugs fouling with soot
carat 3.6
MB Enthusiast
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- In the workshop
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- S124 E300d wagon, W124 om606 monster, E46 v8 coupe
Don't do that, masking one problem by creating another is not a good idea.
Reinstate the filter, accumulator, and make sure both fuel pumps are running. Unplug the 02 sensor at the connection under the carpet in the drivers footwell, and unplug the coldstart injector plug.
Now check the fuel pressure as Grober has said using a gauge teed in the line.
If fuel pressure is ok, remove the cold start injector and check if it is leaking into the inlet manifold.
If all that is ok you'll need to delve a little deeper into the system.
I can tell there is something wrong somewhere as 300-24v's do not run well on a single fuel pump, the fact you drove it like that to your mate's workshop without noticing any issue, tells me the problem was not caused by his work.
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sorry for the slow progress, i have been waiting for an inline fuel pressure guage to arrive. today i have been able to check the pressure. when i ran the engine the guage,which i tee'd into the return line, read 0. i thought, how strange, assumed a faulty guage so took the one from my adjustable fpr and tried again, still nothing. i squeezed the return line and the needle shot up. so basically there is no fuel pressure. i have fitted the aftermarket adjustable fpr and i am able to set it at any pressure i want upto about 60 psi it seems, but i have no idea exactly where i should set it. i suppose the actual answer is to find out why there is no fuel pressure in the first place, i can only asssume the original built in fpr has packed up? seems strange. it doesnt really matter where i set the new fpr, i still cant get a good rev out of it without it spluttering.
grober
MB Master
You need to connect into supply pressure side not the return.
are you sure?, i know my adjustable fpr is supposed to go in the return?
grober
MB Master
http://www.berlinasportivo.com/Technical/lancia/Thema832/Bosch-KE-Jetronic-OCR.pdf
page 10
page12
Basically primary pressure is built up by a restriction against flow and this is provided by the MB primary pressure regulator --- excess pressure not required by the injection system is bled off and returned to the tank----- because its an " open return" there will be flow but no pressure in the return line to the tank.
That's why you generated pressure momentarily in the return line by restricting it when you squeezed it.
page 10
page12
Basically primary pressure is built up by a restriction against flow and this is provided by the MB primary pressure regulator --- excess pressure not required by the injection system is bled off and returned to the tank----- because its an " open return" there will be flow but no pressure in the return line to the tank.
That's why you generated pressure momentarily in the return line by restricting it when you squeezed it.
ok, i put the guage into the supply line and on idle it has 86psi and as i rev it rises to about 96 then comes back down if i hold the revs, its not many ,about 2500.
i guess i need to check if cold start injector is leaking? not sure how to do that
i guess i need to check if cold start injector is leaking? not sure how to do that
Bellow
Hardcore MB Enthusiast
From my manual for K (not KE) Jetronic:
''Primary-pressure regulator The primary-pressure regulator maintains the pressure in the fuel system constant. It is incorporated in the fuel distributor and holds the delivery pressure (system pressure) at about 5 bar. The fuel pump always delivers more fuel than is required by the vehicle engine, and this causes a plunger to shift in the pressure regulator and open a port through which excess fuel can return to the tank.''
5 bar = 73.5psi
'At about' is hardly an exact figure and the pressures may differ K to KE.
so the pressure shouldnt rise as i rev it?
bolide
MB Enthusiast
Never underestimate the complexity of a Mercedes system…
IMHO the problem is likely to be self-inflicted. Something you've moved or changed has caused the fault. Rather than making more changes, reverse each step till you find the fault
Jetronic systems are mechanical computers - every part interacts with every other part and changing anything affects something else. So anything you change may have an unexpected result
Nick Froome
IMHO the problem is likely to be self-inflicted. Something you've moved or changed has caused the fault. Rather than making more changes, reverse each step till you find the fault
Jetronic systems are mechanical computers - every part interacts with every other part and changing anything affects something else. So anything you change may have an unexpected result
Nick Froome
i couldnt agree more that the problems have been caused by making changes, unfortuantly they were a neccessity. Reversing these changes is not really an option any more.
As far as the intelligence of the fuel system goes, and please correct me if i am wrong, from the engines point of view in particular the fuel injection system, the only thing it knows is what fuel pressure is being supplyed, regardless of what is supplying that fuel, or what container it is kept in, or even what pushes it down the pipe. It is either getting what it needs or it isnt?
carat 3.6
MB Enthusiast
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- S124 E300d wagon, W124 om606 monster, E46 v8 coupe
It's a fair bit more complex than that.
What made you fit the fuel cell in the first place? And is that 8mm internal or external braided line? Have you run braided direct to the metering head or joined it before?
Have you reconnected the other pump and accumulator yet?
carat 3.6
MB Enthusiast
- Joined
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- In the workshop
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- S124 E300d wagon, W124 om606 monster, E46 v8 coupe
Keep them unplugged while your fault finding.
Post a pic of what you've done with the fuel pump connections, I'm wondering if you've removed a built in restriction in the fuel feed line when fitting that braided hose. And as such you now have too much fuel flow into the metering head.
In order to check the coldstart injector for leaks, remove it from the manifold but reconnect the feed pipe and electrical plug. Now bridge the fuel pump relay and see if it dribbles.
I changed the tank as the first track session ,and first tyre delam i ruptured the tank. in its original position the standard tank was very vulnerable to exploding tyres.
8mm internal, it runs in one peice from the pressure pump straight to the metering head.
Having been underneath it now i can see what i was told about the pumps is not as it actually is. in the position where the pump, filter and accumulator lived infront of the subframe are both pumps, in line with like an inch pipe inbetween the two. still no accumulator as although i have it, i dont have the pipework to refit it.
Bellow
Hardcore MB Enthusiast
While the (primary) purpose of the accumulator has already been covered - I wonder if it doesn't serve a secondary function of damper. Filling in what would be minute (but tangible) pressure drops and, if, the spring isn't fully compressed at operating pressure, absorbing pressure spikes. The pump, by dint of being elemental must deliver its pressure with highs and lows (which the accumulator could average-out). Could this be impacting on the metering control pressure?
I have been wondering this myself, the only thing that makes me think it isnt the problem is that the car was working very well previously without one, it only had the one pump on it aswell and everything seemed as it was before i messed about with it. i didnt use it much as it had no interior,just the drivers seat, but probably did around 100 miles in total. I know my car, and it was fine. I cant help but think that something has changed while its been away from me. The way it runs now is crazy, nothing like when it left. The black smoke out of the exhaust is ridiculous, the cat is trying to set itself on fire and it wont idle after a mile or so of driving. It cant just be blind luck it worked before. Could it be as simple as someone thinking they were clever has messed about with the mixture screw?
Bellow
Hardcore MB Enthusiast
Wouldn't it have had to be running rough before anyone thought to adjust mixture?
If the lines were broken into downstream from the filter, dirt in the metering unit is what I'd guess - but pray it isn't as I haven't got a clue how to clean that up!
You mentioned having a FPR at hand. Can you plumb that into the feed line and set to 5bar? If so, that would (I think) save the Bosch regulator having to regulate and if things improve then it is suspect. If no improvement then the problem is probably downstream from it.
The fact that you saw the pressure fluctuating is odd. It is (to my understanding) supposed to be constant. Again, this points to the unit's FPR and/or lack of accumulator, though if you drove it there without accumulator I'm less suspicious of its absence.
If the lines were broken into downstream from the filter, dirt in the metering unit is what I'd guess - but pray it isn't as I haven't got a clue how to clean that up!
You mentioned having a FPR at hand. Can you plumb that into the feed line and set to 5bar? If so, that would (I think) save the Bosch regulator having to regulate and if things improve then it is suspect. If no improvement then the problem is probably downstream from it.
The fact that you saw the pressure fluctuating is odd. It is (to my understanding) supposed to be constant. Again, this points to the unit's FPR and/or lack of accumulator, though if you drove it there without accumulator I'm less suspicious of its absence.
