Fuel injector testing

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  #1  
Old 05-19-06, 05:12 AM
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Fuel injector testing

My '88 Grand Prix 2.8litre hesitates and stumbles badly under load, and cranks but wont restart when its hot. When it wont restart, I tested for spark and fuel pressure is 42psi when cranking. I was thinking its the injectors, so I pulled the plenum on the car and measured them.
On the front bank, they read:
11.1 ohms
9.5
9.5
and on the firewall side, they read:
12.2
12.3
12.1
I was hoping I find one or two injectors reading more like 3 ohms making the decision easier. Do you think the front 3 injectors are out of spec enough to cause severe hesitation and starting problems?? Thanks!
 
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  #2  
Old 05-19-06, 07:41 AM
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its hard to say that it would be causing a no start condition but it is probably causing some of your drivability problems would probably replace the 3 below 12 ohms resistance while you have the plenum off.
it is very rare for the injectors to cause a no start condition while its possible due to them all being wired together probably on 1 driver of the ecm not for sure without looking at a wiring diagram think ive only seen it once in about 15 years of working on cars however have replaced many that caused drivability problems such as rough idle or hesitation.
would also like to know if you have injector pulse when the vehicle wont start and even take a fuel sample and probably even pull the o2 sensor to make sure the exhuast isnt plugged before I would be confident that it must be an injector.
 
  #3  
Old 05-19-06, 08:10 AM
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Could it be your coil pack??? those sometimes act irradically when they start going bad. I had a coil once that would cause a miss when it warmed up.
 
  #4  
Old 05-19-06, 08:15 AM
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I checked for spark on one cylinder when it cranks but wont start. A few years ago when I did have a coil, it took out 2 cylinders but the car still started. I also have good fuel pressure when its cranking but not starting. (42psi)

Based on the resistance measurements I got above, you think they are out of spec enough to cause a no-start condition?? Thanks!
 
  #5  
Old 05-19-06, 09:46 AM
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they are out of spec and should be replaced whether it is causing your no start dont know nor will anyone without actually looking at the car. you should always check for spark on 2 or 3 cylinders on dis cars with multiple coil packs.
the resistance of the injectors can vary based on temperature and load one of them may be going much lower than what you are reading on your ohmmeter now.
 
  #6  
Old 05-20-06, 05:18 AM
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Originally Posted by George2002
Do you think the front 3 injectors are out of spec enough to cause severe hesitation and starting problems?? Thanks!
No.

How's this thing idle?
Hard hot restarts may be caused by a leaking injector. With the fuel pressure gage connected, does it maintain pressure after you shut the engine down? It should hold within 10 psi or so for fifteen minutes. If it falls to zero within say 30 seconds, you've got a leak somewhere, could be injectors, pressure regulator or fuel pump. One way to check the injectors would be to pull the fuel rail and injectors out intact and still connected to the fuel lines, and then turn the key on to pressurize the system, and watch the injector nozzles for drips, or spray depending on how badly they are leaking.
 
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