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Join Date: Dec 2000
Location: Aiken, SC
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Question fuel delievery problem

ok 87 944 n/a

here's what the problem is.
one injector is not getting enough fuel.
the injector near the front (cooling fan side) doesn't seem to be getting enough fuel, I have tested the volts to the injector >OK<
I have tested the resistance of all injectors (I was told reading should be around 2-3 ohms) all tested ok with same resistance around 2.5 ohms.
When the car is started you can tell it's lacking fuel, idle around 700, If I disconnect the first 3 injectors (one at a time) the engine rpm drops (normal), when I disconnect the 4th injector (front one) no change in engine rpm.

I have recently replaced a bad DME/Fuel relay.

Have not checked the amount of fuel being pushed to the rail from the pump yet.

There only seems to be a fuel delievery problem at that end of the rail (front).

Does this sound like a fuel pump going/gone bad?
Or something wrong with the fuel rail?

looking for which way to go before replacing parts.

sorry if post is confusing......

if you need anymore info let me know.

Thanks
Rob
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Rob
87 944 * 89 951
"When I die, I want to go peacefully like my Grandfather did, in his sleep -- not screaming, like the passengers in his car."
Old 04-29-2003, 07:02 AM
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Ok, Rob, there are several things you can do to pinpoint your problem.
  • Firstly and foremostly you need to do a compression check. Proper functioning of the L-Jetronic/Motronic system is dependant upon the soundness of your engine.
  • Pull your injector rail with the injectors still attached. Take a 9v battery with two jumper wires and touch them to the suspected injector's contacts. you should get a nice spray of atomized fuel. Do it in a cup or something because if your atomized fuel gets into the dist....bango.
  • Obtain a fuel pressure gauge if you get good spray (or even if you don't, they are real handy at diagnosing your fuel system. Get specs from manual and run pressure and volume tests.
  • If you still have a problem, remove your TDC and RPM sensors and make sure the bottom hasn't gotten fouled with little bits of metal or somethin
I hope I've helped.
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*Disclaimer: The person above is actually dumber than he appears.
my web site Torque values maintainance and repairs lots of my rebuild pics weights and measurements
'84 944 auto/ps/ac/cc
'86 951
Providing ignorance one post at a time.
Old 04-29-2003, 09:37 AM
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Talking Thanks Todwic!

1. compression over all 4 cyl= 150
2. happened to check condition of plugs......
two plugs were fouled , replaced the set.

for *****s and giggles put new ones in and cranked her up.

whoa idle is smooth around 900, checked injectors, pulled power from them one at a time, sure enough when each one was pulled idle dropped like it should. The front injector that was in question was operating without a problem

to sum it up..
thanks todwic for you help, without starting with comp check never would have looked at plugs.

Is this common when plugs are fouled fuel distribution also goes south??

just when I think I am getting comfortable with repairs little things like this knock me back down

all seems well running smooth not missing a beat!!

thanks again

rob
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87 944 * 89 951
"When I die, I want to go peacefully like my Grandfather did, in his sleep -- not screaming, like the passengers in his car."
Old 04-29-2003, 04:07 PM
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Nothing was wrong with your fuel dist., that cyl wasn't firing, it was getting fuel. An addition to the pulling power off of inj. one at a time is you can swap leads between injectors, which will help you rule out whether or not the inj. is getting pulse or not, such as with a faulty connector. Fouled plugs are sometimes indicative of another, sometimes larger problem. Your comp. is good, perhaps you need to widen your plug gap just a tad. AF Juvat could help you better in this area (hotter/colder plug, bad fuel/need to run inj cleaner, etc)

People often fault the injection system first because it's the "new" item, when it's a more simple matter, such as your case. (would you first have faulted the carb were your car so equiped?) Sorry, I don't mean to lecture, glad you found your problem!

__________________
*Disclaimer: The person above is actually dumber than he appears.
my web site Torque values maintainance and repairs lots of my rebuild pics weights and measurements
'84 944 auto/ps/ac/cc
'86 951
Providing ignorance one post at a time.
Old 04-29-2003, 05:00 PM
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