Pulled the PITA Lingenfelter intake to check for pinched wires to the FIs. Maybe relieved it, but I started checking resistance to ground in a number of places, with my digital VOM. I NEED to ensure of a fix before reassembling it. (FelPro should make Velcro gaskets for this unit.)

I'd just driven the car after having this intake off/apart for another issue, parked it -- No start after about an hour; code showing the short, as above.

Comparing the L/R side ohmages, ( no tech detail of that sort is available to me) the L side was near zero.Pulled only #1 & 3 inj plugs (only ones accessible, w/o further disassembly); both checked around 15 ohms, as did #7 & 8. Those plug lead's resistances matched also, UNTIL I checked with #3 plugged to its injector, whereupon it dropped from the 5.4 ohms, to 4. That would tell me the injector is shorted, IF it hadn't checked at 15 ohms! With four (each side) injectors connected in parallel, as they are, the theoretical resistance would be 3.75, reasonably close to the observed, given the unknowns in the remainder of each (L/R) circuit.

I must be missing something here; comparable readings everywhere and the 'problem' injector testing okay as does its plug,...

Are there resistance specs or procedures that differ from what I have tried? thanks for any support.

MORE: I felt I was doing a poor job of explaining.

The fuses are out, disconnecting the power, but the ECM is connected. I was hoping to find the short an easier way.

I took comparative measurements with all injectors plugged in, one off, and two off. The odd thing is how all comparisons matched, until the #3 injector was plugged in; again, that injector's resistance was about 15.

I did not check any resistance at or of #2,4,5 or 7, as I'd found an anomaly at #3 and b/c they'd require pulling the runners for access, due to the design of this manifold.

As expected, disconnecting one injector on the 'good' side, increased the measurement, to a value identical to the 'bad' side. That seems to indicate that the problem is not with the ECM, the wiring to it, or with the other injectors and their connections.

With the injectors wired in parallel, isolating the short may be a visual task. I guess it's possible that the ECM connection may alter the comparison readings, but I bumped the starter as a check, with no change in the readings.

check your injectors hot.. if any are 12 or under there is a turn to turn short in the coil.. only choice is new injectors..

And if you need new injectors FIC is the best place to look. They are a sponsor here and we support them not only because they're sponsors but because they're damned good at what they do. Great customer service and support before, during and after. My 90 and 91 both sport FIC products.

thanks. Checking them when hot will be nigh impossible given the hours it takes to pull the intake down far enough to get access to them.

After another look at things (fresh eyes you know) I moved the seemingly pinched wires for 5 & 7, rechecked for shorts to ground (none) then inserted new fuses. Powering up the ignition did not blow either fuse, so I made new gaskets, readying for reassembly.

These injectors are about 10 years old and have under 5000 miles on them, I estimate. It seems I have two choices:
1) send the set to be checked thoroughly, or
2) reassemble and hope the repositioned wires fixed the problem.

Injectors are amazing looking and the test report is great, now. Now installed, wires routed carefully, the rail won't hold pressure, tho I cannot get the pump to continue to run past the 5 second key-IN, using the ALDL connectors.

RC, in Torrance, CA are friendly and do what they promise; report these are Bosch. I need to get the Vette running and moved, so I was nudged into a local, reputable firm.

I'll have to jump the relay to run the pump long enough, before reassembling the plenum.

You need to do a leakdown test as described in the FSM. Did the rail hold pressure before the removal?

thanks for the support.

The prior leakdown was slow, but definite.

Current leakdown is much worse, plus the short moved from the left to the right side. Shop offered to retest the injectors, saying they twice-test them for shutoff. I think the issue is electrical, allowing fuel flow continually; the worsened leakdown explained by the improved flow and underscored by strong gas smell in the runners, despite no crank.

Close inspection of the wires, after rail removal showed a few places where wires were compressed and one small crack in #4's; repaired.

Resistance is infinite on both FI leads with fuses pulled and injectors disconnected; a good sign.

I received a small part (thx, RC Engr.) late yesterday required for reassembly, will restart that process today, after checking the fuse > ground and > FI socket integrity.

Hey, at least the audio system I retrofitted ROCKS! Nice massage from the bass, too.

My car's fp leaks down as well. That is with a walbro pump, rebuilt 30 lb injectors, new fpr. But runs great anyway. I think mine is due to the aftermarket pump, perhaps the check valve in the pump is different or non-existent. Don't know for sure, but not a big deal since it runs well.

If you are concerned about the fuel injectors themselves leaking down then you can pinch off one of the hoses near the gas tank to verify. The steps are in the fsm and I have them posted in a thread from the past if you search.

There is also a way to power the pump with a jumper wire from 12v+ battery to one of the aldl ports....I can't remember off hand so I'll have to look it up.

Also, I am able to pull the injector harnesses off the fuel injectors while my SR is installed, so not sure why you can't? I use a long screwdriver to help push the metal connector then pull it up.

Quote:Interesting. It is hard enough to get half of them off, even disassembled. Perhaps your leads are longer. I can get four off, with it installed.

I have the rail back together and am about to pressurize it. No shorts to ground show up and all injectors test slightly >15 ohms. I checked fuse feed lead to ground on each bank as I reassembled, then rechecked both sides after. I'd gotten no grounded readings from any injector connector with them removed and the fuses out, so I believe my ECM is not shorted, either.

I powered the FP via the relay, last time, which I find easiest, having them mounted upper left, clamshell aft.

Thanks for hanging around this thread.

I really think you need to call John or Rick at FIC. They have a toll free number. alook at their info in supporting vendors on the left side of this page. Their service is absolutely the very best.

WhalePirot - Where are you? I am in San Pedro! And used to live in Torrance. You will have to come to one of our SoCal Socials! Keep an eye out, one is coming SOON!

Appreciate the input, guys. Encouraged (and tired of this) by the leakdown comment by Matatk, I reassembled it all. While not sure if it is good that I can do it must faster.

The car runs, though there is a miss I need to trackdown.... tomorrow.


Bogus, I am in Mission Viejo.

You guys may like hearing that I am building a '55 F100 that sits on its original chassis, but has full '84 Corvette suspension with coilovers and poly bushings. The original L83 (now a 383) from my 2nd owner, Shinoda-bodied Vette, powers it through a 700R4 to the 3.07 rear. It should be a nice cruiser.

As far as your superram, have you converted those 12 pt head bolts to allen caps or studs? Makes install/removal easier.

The other project sounds very cool. Another member here and buddy of mine (hdfire) is building a 57 chevy stepside with a camaro suspension graft and a zz4/400 turbo combo. I love all of those old trucks.

Also, as far as the aldl, it is port G to supply 12v to in order to power the pump. If you choose to go that route.

Quote: All bolts in the SR are Allen, always have been. A (hack) shop, Sevens Only racing, in Buttonwillow, really F'ed up this engine and drilled the SR base through, using bolts under(outside)it which is faster for re/dis-assembly.

Mission V! Ok, cool! Keep an eye out for our next Socal Social. We have had, in the past, upwards of 12-15 folks. Great fun!

The next one will be on a Saturday, and might be a late lunch thing, so isettr1 can come down from B-field.

Quote:

Not sure I understand this....the bolts for the plenum "pizza box" part have always been installed from the bottom.

Keep an eye out for our next Socal Social. Where is that posted? Perhaps I will have a running car by then.

Not sure I understand this....the bolts for the plenum have always been installed from the bottom.

Originally yes, but the 'so-called professionals" at Sevens Only, truly hacks, in reality, drilled through, such that allen-head bolts, inside, are nylock bolted underneath. Yes, there is minor risk in hardware entering the intake; very minor with good hardware.

Okay, I smell like exhaust again!

Got the wife's project car running well, so I did more research and then some Corvette checking. The car runs, tho not real well. I think some of that is remapping the fuel tables with the redone injectors, and it has improved overall, but (as usual) the hot idle takes the longest and affects the drivability, most; quitting at stoplights, etc.

The electrical is frustrating, given the low ohmmage of the injectors and the parallel circuit, but I believe that's the issue. The spark is okay on all 8, hard as it is to pull wires. My trusty inductive timing light is failing, but is the easiest way to check for spark.

#3 is weak, evidenced by no RPM drop with the wire pulled and the plug looks brand new; surely not firing with no fuel smell. That injector has 12vdc with the key ON. #1 plug has some rich fouling, due, I surmise, to the injector renewal flowing more.

The miss, not easily discerned due to the aggressive cam profile, is most apparent under acceleration. If the inexpensive IR temp reader is accurate, the left side exhaust runs 100 or more degrees cooler. I listened for clicking on each injector with my stethoscope. The right side units clicked more loudly. I could hear plenty of noises on the left but little or no injector rat-a-tat as they open and close.

I just realized that if the left bank was shorted to ground, the injectors could be always ON, allowing fuel to always flow, which would explain the low left exhaust temps, explain the partial carbon traces on some plugs, allow some power from that side and thence, a weak indication of miss in the exhaust note, yet a definite loss of power overall. It would also explain the lack of fuel pressure holding after shutdown.

Back to the electrical: four 15 ohm loads in parallel is 3.75, barely above a short. I recall one reply about disconnecting the ECM and checking again. I resisted having to do that; a chore of discomfort.
More later.

Sorry if I forgot since I haven't read the thread in a while...did you check the injector pulses with a noid light?

On a side note regarding the SR bolts....it is common to drill the holes for different hardware. Since yours is already drilled, consider drilling and safety wiring the screws/bolts from the inside of the plenum.

Quote:No, I tool a breather and had not posted, hence no activity. thanks for returning.

I need to learn if the noid lights, which I have not used, will do anything that a test light or DVOM cannot. The test light just stayed on when clipped to 12vdc; the probe on the ECM fed wire with no pulsing. Past experience showed me a DVOM is not too helpful for the quick pulsing, tho. Then, no digital gauge is readable with rapidly changing values.

I know they're more convenient.

I would use the noid lights...that is going to tell you if there is an injector signal...you won't really get that with the dvom the same way. You can rent them at autozone or buy a set for about $25.

Since you think there is a short, I think it's important to isolate the injectors from the harness in that circumstance.

Matthew

thx.. I am all over amazon, now.

Quote:This is a public thank you for their phone support; not recommending a replacement ECM until more troubleshooting, with specific recommendations.

Also rare, is the kudos for the (sort-of )competitor FI cleaning/checking service I used across the USA from them, but local to me. Incompetent shops deride others' service.

John runs a good firm. They are realistic and responsive to the customer. No question.

Of all the internet based parts firms, FIC and RockAuto seem to have the highest customer satisfaction - in short, no one has ever really complained about either.

I have used Jon for both a new purchase as well as rebuild/cleaning service and was very pleased both times with the quality of parts and customer service.