impossibly high fuel pressure?
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impossibly high fuel pressure?



Hello All,

in my quest for getting my car started again, i was fortunate enough to find 
a kind soul on the DML who sent me his pressure testing kit so i could check 
my car out. here is what i found:

engine will crank, turn over, and spark. fuel is getting to the cylinders, 
about one drip every two seconds. frequency valve is working and the cold 
start valve works correctly.

resting pressure - 2.75 - 3.5 bar

pressure upon jumping the RPM relay for the pump - 7.5 - 8.0 bar. fluctuates 
about twice a second between those numbers. bad pump?

pressure upon turning ignition key and trying to start - about 6.5 - 7.0 bar. 
jumps around.

here are some notes i should relate:
1. my fuel pump through this whole ordeal has been making sick noises. it 
has been sounding like it fluctuates in pitch. it sounds like rrooowwuh, 
rrrooowwuh, rrooowuh. you get the picture. it is not a steady noise like a 
fan. i understand this is wrong. so i disconnected my pickup hose and since 
my gas is so high in my tank (about 4/5 full) i was able to drop my fuel pump 
in and it was partially submerged. i then jumped the pump and it sounded 
better for a few seconds, sounding like it should, but then it gets worse, 
but never as bad as with the hose. so i probably have a broken/collapsed 
hose. ok. but that doesn't explain the high fuel pressure.

2. when my car first started this situation, i pulled the pump to clean it 
up. i found that a previous owner lost the rubber cover for the pump and 
there was now a good inch of murky water in the boot, covering the terminals. 
i removed the pump, cleaned it, and let it dry. my dad and i tested the 
pump by hooking it right up to a battery and ran it dry for about 5 seconds 
at the longest. this was probably dumb, but too late. could this have 
damaged my fuel pump so severely that it would have no internal regulation 
what-so-ever?

3. if the pump were indeed bad, that doesn't answer the high pressure 
question. let's go back to the function of the primary pressure regulator in 
the fuel distributer. this part is supposed to regulate the system pressure 
from the distributer onward. it functions by throwing out extra fuel to the 
return lines, and only keeping enough fuel to go through the feed lines which 
correspond to the correct pressure for the fuel injection. i understand that 
the fuel pressure is within specs if it is between 4.8-5.5 bar, in those 
whereabouts. target range is 5.1-5.3 bar. if my pressure between my fuel 
distributer and my control pressure regulator is a whopping 7.5-8.0 bar, that 
would imply that i have ABSOLUTELY NO REGULATION AT ALL through my entire 
system. therefore my fuel distributer failed overnight and the primary 
pressure is faulty.

4. however i do not believe the above situation has occured. i removed the 
spring and bolt pieces from the fuel distributer (the actual heart of the 
primary pressure regulator) and lo and behold, they where clean as new, with 
absolutely no signs of wear or damage. there were no metal shreds or 
anything in the gas that came out when i pulled the spring out. i do not 
believe my primary pressure has failed. something else is very wrong. also, 
according to DMCJoe and Steven Wynne, there has never been a known case that 
they have come across of this part failing in this manner. NEVER.

i am really throwing my hands up in the air on this one. it seems i have an 
impossible problem and i've done everything i can to diagnose it with tools. 
the only thing else to do is to start swapping very expensive parts just to 
'see if it does the trick', however i do not have that kind of money. 

anyone out there have any good ideas on what my problem could be?!?! you've 
all been very helpful in the past on this problem, but i keep on finding out 
that what i just tested isn't the problem. i've got impossibly high 
pressure, assuming the primary pressure regulator is functioning, and there 
seems to be no explanation for it.

i heard Marty Maier (sp?) rebuilds fuel distributers. maybe he can help me 
out? if the moderator could CC this message to him, that would be very 
helpful i think. 

any ideas out there????

Andy

Soma576@xxxx
1982 DeLorean DMC-12 VIN#11596
Fargo, ND 58102


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