94Q Injector resistance???

[wamQ45]

I just removed my plenum to do a "hose job" (I kinda like the sound of that) and I checked the injector's resistance. All were 11.4 to 11.7 ohms except one it was 10.1 ohms. Is this considered out of spec????

[Q45tech]

The injector solenoid is just a coil of wire with 12 ohms resistance [varies slightly with temperature and the cost and accurracy of the ohmmeter you use to test]. Corrosion on the terminals can only make the reading higher so a lower reading is from something dissolving the varnish type insulation on the wire allowing two adjacent turns to short together thus lowering the resistance.

1 ohm from the average is surely significant.

A shorted turn will affect the magnetic lifting strength of the pintle thus slow the opening time against the 34-44 psi fuel pressure.

The leaness is most critical at idle as it it already super lean normally.....less than 10% less fuel will cause the cylinder to miss fire.......depending on spark plug condition.

The power balance mode test on the Consult tells you the effect of shuting down the spark and injector or a cylinder by cylinder basis. A 12 rpm variance is good, a 25-37-50 variance means a significant variance in the power output ......the more the less smooth the idle and probably cruise and surely less full power!

[wamQ45]

I took new (more accurate) measurements with my TPI 440 Scope Plus. This is a spendy little multi-meter/toy. The results are as follows.

1. 11.2 ohms OEM injector2. 11.5 ohms Replaced injector (replaced by myself)3. 11.5 ohms Replaced injector (repaced by dealer b4me)4. 11.2 ohms OEM injector5. 11.5 ohms Replaced injector (replaced by dealer b4me)6. 11.1/2 ohms OEM injector7. 9.8 ohms OEM injector8. 11.2/3 ohms OEM injector

[Q451990]

I know you probably already thought of this, but I'd swap #7 with #2 (since it's newer than #1). That way you can easily replace it if it get's worse or completely craps out w/o removing the plenum. Just remember to replace and lubricate the o-rings on anything your move.

Heath

[Q45tech]

Always make sure the rails are dry as I have seen engines hydrolocked by forgetting this step and the rail emptys gasoline into the runner......reassembled with new injector [then cold start enrichment] whamo bent rods.The cylinder volume is 561 cc and the head volume is 55 cc.....60 cc of fuel [2 ounces] might be enough!

[wamQ45]

Yes, my plan was to move two of the old injectors to #1 and #2. With replacing #7 this would give me a total of 4 replace with the probability that 4 others could go bad. That's 50% chance that a bad OEM one would be accessable. Thanks on the o-ring tip I would not have thought of replacing them.

[wamQ45]

Q45Tech,

How do you empty the fuel rails??? The last and only time I replace a fuel injector I just pulled out the old an put in the new. Also, what should I lube the o-rings with?

[Q45tech]

You pull the pump fuse and let the engine die when the rails run dry!

[wamQ45]

Too late the plenum is off....Is there a method other than sucking the gas out that will work.

[Q451990]

I'd pull the fuel rails and replace them that way. I've never had much removing injectors without destroying them (prying them out with a big screwdriver or twisting with big pliers) but it's probably easier being able to gently push up on the pintile end.

If you don't want to take the rails off, you might be able to remove the hose connecting the two rails and let most of the fuel drain out. Be sure to loosen or take the gas cap off. I had a nice puddle of gas in the "valley" once from the expansion of the fuel while the gas tank heated up in the August sun...

The o-rings can be greased with vasoline. Some say di-electric grease is better. The goal is just to make sure you don't pinch the o-rings and let fuel leak down into the cylinders and create a flooding or hydrolock situation!

Heath

[wamQ45]

Well I got the fuel rail off but can't get the fricken injectors out!!! I found a local facility that will clean the injectors so I figured that I might just take the both fuel rails to them and have them do it. Also, will be replacing the seals between the rail and intake.

[rod_ontario]

I used a #11 socket (sears brand) and a small vice with a 2” spacer. This worked well.I have attached a photo of the setup I used.

[DAEDALUS]

A shorted turn will affect the magnetic lifting strength of the pintle thus slow the opening time against the 34-44 psi fuel pressure.

I thought the injectors didn't have pintles (???). I'm only asking because I'm considering buying an injector tester that has a long probe that senses the pintle's vibration. I thought maybe it wouldnt' work on the Q's injectors. Let me know what you think.

[Q45tech]

Use a current probe around the positive lead [the ecu grounds the injectors] [make a loop of wire for the injector circuit fuse -common to all 6 or 8].Drive the time base from #1 voltage. Each injector is open from 2-10 milisecs, that is the current/voltage flows for that long but the start of ramp to the pintle movement takes about 1 millisec.Look at the waveform on oscilloscope it shows 8 ramps [in the order injectors open] , each ramp containns a tiny squiggle 2/3 of the way up showing when the pintle lifts off the seat.

All the current peaks should be the same, if the resistances are the same.