Fuel injector questions
Fuel injector questions
Hi everyoneHere is the problem.I got the check engine light on my J with 145,000 miles. ECM shows 51 injector circuit. I narrow it down to #6 injector is open, #2 is out of spec 23.2ohm. The rest of the injectors are with in spec 11.2 ohm(#1,3,5 an 6). The ohm test is done when engine is cold.My questions are1) Should I replace all the injectors at once since it is labor intensive to pull the plenum? Unlike the Q,none of the injector on J can be replaced without remove the plenum.2)If I just replace #2 and 6 injectors and then perform fuel rail/injector cleaning plus new fuel filter. Would the process increase #1,3,5,6 injector life or the damage is already been done ? 3) What are the relationship btw the injector resistance and injector efficiency? In other word, partially clogged injector will have higher resistance?4) Any other advice regarding to this issue?Thanks a lot!!!
1) It really depends on how much your time and labor are worth relative to the cost of the parts, plus your estimate as to the risk of not doing them. Your injectors are probably the same as the Q's in cost...about $140 each. In the 4+ years and 40k miles I've owned my Q, I've only twice had an injector fail on me, one of them just a few months ago. And I live in a so-called bad gasoline (RFG) state. No other injectors replaced according to the service history. I'm certain that the 2nd time you pull the plenum will be tons easier than the first. I keep a spare injector in the trunk, along with my tools.
2) Injectors fail in 2 distinct ways--either a circuit failure (the code you got) or by clogging. Cleaning will help the 2nd mode, but I don't know if clean injectors last longer or not. Certainly if there's any physical damage to an injector, such as worn insulation or a cracked wire, no amount of cleaning will help at all.
3) I *think* very little relationship within the 10-14 ohm spec. At 23.2 ohms, I'm not sure what happens...maybe decreased firing time? Perhaps Q45tech can quantify any relationship. Again, clogging has no effect on resistance.
4) In regard to your #2 injector, verify that it is the injector that is high and not just the harness. I know of one Q's harness that is high on 2 injectors, but the injectors are fine when ohmed directly. Definitely a cheaper and slightly less labor-intensive fix!Though it won't fix a bad injector, a cleaning is not a bad idea. I just flushed my fuel rail Monday night and my car runs real smooth now. There was an infrequent but noticeable slight roughness at idle before, and that's completely disappeared. Looking forward to doing a fogger intake cleaning soon as well.
2) Injectors fail in 2 distinct ways--either a circuit failure (the code you got) or by clogging. Cleaning will help the 2nd mode, but I don't know if clean injectors last longer or not. Certainly if there's any physical damage to an injector, such as worn insulation or a cracked wire, no amount of cleaning will help at all.
3) I *think* very little relationship within the 10-14 ohm spec. At 23.2 ohms, I'm not sure what happens...maybe decreased firing time? Perhaps Q45tech can quantify any relationship. Again, clogging has no effect on resistance.
4) In regard to your #2 injector, verify that it is the injector that is high and not just the harness. I know of one Q's harness that is high on 2 injectors, but the injectors are fine when ohmed directly. Definitely a cheaper and slightly less labor-intensive fix!Though it won't fix a bad injector, a cleaning is not a bad idea. I just flushed my fuel rail Monday night and my car runs real smooth now. There was an infrequent but noticeable slight roughness at idle before, and that's completely disappeared. Looking forward to doing a fogger intake cleaning soon as well.
DAEDALUS
Walk me through the fuel rail flush you mentioned.
On every car (not just the Q) where I needed to pull the fuel rail or injectors, I've usually treated the injectors like a farm-fresh warm egg and basically tried to handle them as little as possible for fear or screwing something up.
What would I do to "clean" the fuel rail and injectors beyond just using a gas additive?
Dan
Walk me through the fuel rail flush you mentioned.
On every car (not just the Q) where I needed to pull the fuel rail or injectors, I've usually treated the injectors like a farm-fresh warm egg and basically tried to handle them as little as possible for fear or screwing something up.
What would I do to "clean" the fuel rail and injectors beyond just using a gas additive?
Dan
It's not purely a DIY thing. You'll see some references on this site to a "BG" rail cleaner. It's a piece of specialized equipment that allows you to pump a cleaner through the rail and run the engine off of it. I just picked up a similar device...basically it's a cannister that has a pneumatic hose connection on top with a pressure regulator. On the bottom is another hose with a valve. You pressurize the cannister...adjust the regulator till it's running a little above normal working pressure. I felt 52 psi was safe, and this higher pressure is one benefit you don't get with a gas additive. Clamp off the rail return line, open the cleaner valve, and start the car. It runs for maybe 20 minutes, depending on how much you play with the throttle. No need to pull the injectors or mess with the rail...all the connections are made on the fuel lines. The solution is available commercially.
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Q45tech
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- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
52 psi is good because 99% of the time the injectors are seeing only 34 psi [at idle and cruise] and 44 psi only on WOT........but 52/34 SQRT =24% higher flow so the 11 ounces goes faster by 1/4.
The BG system can hold about 22 ounces so sometimes I add a little gasoline or other chemicals [xylene/toluene] to give the full 20 minutes at the higher pressure.
The BG system can hold about 22 ounces so sometimes I add a little gasoline or other chemicals [xylene/toluene] to give the full 20 minutes at the higher pressure.