Re: impossibly high fuel pressure?

[jtrealty@xxxx]

Refer to parts manual 2-1-0 part # 14 or 102359 fuel pipe. Follow to 
fuel distributer and remove at the fuel distributer. Hook a temporary 
pipe onto the fuel distributer and place the other end in a pail to 
catch the fuel. Run the fuel pump (jump the rpm relay) and read the 
PRIMARY PRESSURE. (Refer to workshop manual D:02:02 for correct 
procedure). It is possible for a problem in the control pressure 
circuit to cause primary pressure problems like an eroded restrictor 
but I don't think that is the trouble. Until you can get your Primary 
pressure under control don't worry about control pressures. Although 
you ran a flow test to the tank I think you have a problem with the 
return hose and even though you got good flow at the tank it had to 
get past a restriction that is causing high pressures at the fuel 
distributer. By disconnecting the return at the fuel distributer you 
will be "bypassing" any restriction and allowing the fuel to dump 
letting the primary pressure regulater work. Since you are deep in the 
fuel system I recommend you go to www.motorbooks.com and order book # 
112910A for $29.95 Bosch Fuel Injection Handbook and Engine 
Management. It gives a very in depth description of the operation of 
the K-Jetronic fuel system and troubleshooting procedures. Be careful 
in getting advice from people not specific to the Delorean. There are 
slight changes in the fuel systems from car to car and what may be 
valid for a Volvo for instance may not be true in a Delorean. The 
Primary pressure regulater sets system pressure so if it is too high 
it is only because it is not sending excess fuel back to the fuel tank 
for whatever the reason. A failed cpr should not increase the system 
pressure although it can reduce it.
David Teitelbaum
vin 10757


--- In dmcnews@xxxx, Soma576@xxxx wrote:
> Hello David (and the rest of the list), 
> 
> you have so many things to say, i'll just answer each part 
individually or 
> else we'll both get very confused!!
> 
> n a message dated 4/10/01 9:21:40 PM Central Daylight Time, 
> jtrealty@xxxx writes:
> 
> << > Before you give up I have some ideas you can try. If indeed 
your 
> > primary pressure is too high besides the primary pressure 
regulater 
> > being stuck (which you say isn't) >>
> 
> i have pulled the bolt and spring/pin assembly. the whole thing is 
very 
> clean with no corrosion or debris. the pin in the spring moves 
easily, and 
> the hole in the bolt is not plugged from either direction. so i 
must assume 
> that this piece functions correctly. after all, there's hardly 
anything to 
> fail, except for the diaphragm inside the fuel distributer.
> 
> 
> <<another possability is a restriction 
> > in the return line from the regulater to the tank.>>
> 
> from the fuel distributer to the tank, everything is kosher. 
remember? we 
> put a bucket around the return line in the tank and we measured out 
the 
> correct amount in one minute (2 liters) as stated in the shop 
manual. i also 
> removed the return line from the control pressure regulator which 
goes into 
> the side of the fuel distributer. i ran the fuel pump and fuel 
flowed out 
> very freely, without sputter or dripping. this says that the 
control 
> pressure regulator is not plugged on the return end, correct? i 
would assume 
> so.
> 
> << Since your resting 
> > pressure is about right the fuel accumulater is probably OK.>>
> 
> i would be inclined to agree. 
> 
> 
> <<A quick 
> > and dirty test is to remove the return line from the regulater and 
rig 
> > up something temporary into a pail and see if the pressure is now 
in a 
> > more normal range. >>
> 
> can you describe this in greater detail? i don't know if you are 
talking 
> about the return on the control pressure or the primary pressure. 
and when i 
> remove it, from what end of the hose? if you could get more 
specific, i 
> might be able to see what you mean, and maybe i've already done 
that.
> 
> <<I think the noises from the pump are just it trying 
> > too hard against the high pressure, after you can get the pressure 
> > right the pump might be alright. >>
> 
> that would make sense if the INTAKE side of the fuel system were 
plugged. 
> however the fuel pump is capable of putting out over 120 PSI of fuel 
pressure 
> (typically they are twice as strong as the system requires), so i do 
not 
> think the pump is strained. i was reading about 7.5 bar of 
pressure which 
> is around this PSI level. i believe the pump is as strong as it 
should be, 
> but it might not be CONSISTENT!!
> 
> <<If you cannot regulate the primary 
> > pressure don't bother checking the control pressure, it will be 
too 
> > high also, it also dumps into the return line to the tank and 
besides 
> > it receives "regulated" presssure from the primary regulater so if 
> > that is too high the control pressure reg can't reduce it enough. 
>>
> 
> this is what i believed about two days ago. however i have since 
talked to an 
> engineer at bosch and a K-Jetronic guru at a local import dealer 
here, and 
> they both say that it is possible to read pressures in excess of 6 
or 7 bar 
> due solely to a failed control pressure regulator. the primary 
pressure 
> regulator may be working just fine, however it is possible to get 
too high of 
> pressure AFTER the primary pressure. i don't really understand it, 
but both 
> of these guys insisted that the control pressure regulator is at 
fault. the 
> guy at the import dealer noted that i said my system pressure was 
measured at 
> about 6.5 bar today and my control pressure is at 3.5 bar on a COLD 
ENGINE!!! 
> this is definitely not right he said, and the problem lies within 
the warm-up 
> regulator (CPR to us DMC guys). the problem is the difference 
between the 
> system and control pressures is too narrow. the warm up pressure on 
a cold 
> engine is spec'd at around 1.5 bar (i don't see that spec in the 
shop manual, 
> but he insisted that all of these systems are the same, even on the 
> DeLorean), while the hot running temp pressure is supposed to be 
around 5.1 
> bar. you see the vast difference between the cold and warm 
pressures? he 
> insists that this is the problem. he says that if i replace my 
control 
> pressure regulator, my overall system pressure will stabilize and 
things 
> should be close to perfect again. however, after all of this 
pressure shock 
> to my fuel system, i may need to add or remove a couple shims on my 
primary 
> pressure. this weekend i'm borrowing a fuel pump and CPR from a 
couple kind 
> DML'ers and i have a feeling i will have a few more questions 
answered this 
> weekend... and i'll be sure to post to the list what happens. 
> 
> if you or anyone else have any ideas, let me know.
> 
> Andy
> 
> Soma576@xxxx
> 1982 DeLorean DMC-12 VIN#11596
> Fargo, ND 58102
> 
> 
> [Non-text portions of this message have been removed]