"Parping" from 3500rpm up on secondaries...

[XfireZ51]

Ask Pete what happens when your motor heats up to 261.

[Dynomite]

Originally Posted by XfireZ51

Ask Pete what happens when your motor heats up to 261.

Well? Is this assuming coolant boiled off and water pump cavitated....then things went South quickly?

So.......how bad can it get? And how did Pete's situation happen?

I thought I had the rarest. New water pump. Fired it up and went for a drive....impeller spun free of input shaft on new water pump. I caught the temps before they got into red zone.

[c4koh]

The engine got to 260 for not more than 10 minutes, and I can't be sure it was that hot when driving it. Coolant was always fine (water never boiled off).

In any case....

Suspect #1 from the threads above re: injectors. I just went and tested the resistance across all of them, and...

(I read it should be 12.1ohm +/- 0.1ohm at 68F. Today was 90F (the engine probably a bit warmer too, as I tested about an hour after a short drive to get coolant to 210), and none checked out at 12.1ohm, the "good" average seemed to be 12.9ohm. My notes on this (I think they're from Marc Haibeck) notes that 13.5 around 30 minutes after warm is a good average, so I presume my 12.9 is about right given the time/temp.

For reference:
PRIMARY INJECTORS
#1 12.8 ohm
#2 13.0 ohm
#3 5.8 ohm
#4 12.9 ohm
#5 13.1 ohm
#6 13.0 ohm
#7 12.8 ohm
#8 12.9 ohm

SECONDARY INJECTORS:
#1 6.3 ohm
#2 0.7 ohm
#3 11.4 ohm
#4 3.4 ohm
#5 6.3 ohm
#6 12.8 ohm
#7 8.7 ohm
#8 5.9 ohm

As can be seen, Primary #3 looks bad, and pretty much all except #6 of the Secondaries look poor!

So certainly will replace these, and while under the plenum fix the vacuum leak. I hope that with no evidence (so far) of white smoke, oil in coolant, and coolant/froth in oil, that hopefully (fingers tightly crossed) that the rumbling is just a mis-fire from the injectors not fully functioning...

This being said, for my own interest and knowledge (will try and look up the answer in the meantime):

A "bad" injector (concluding it's bad from the off-par resistance) still functions, just badly, right? And perhaps in my Secondary #2 (resistance at 0.7 ohms) it's just shot?
When they're "shot" - do they let in any fuel (as basically drips rather than nice injected spray) or do they simply clog up and not allow anything.

Still unsure why the car drives fine and powerfully until it's at least warm, and seemingly with no problems (and very, very fast) with POWER KEY on.

Thanks all so far for the help. Will report back once I've replaced the injectors.

[We Gone]

Originally Posted by Dynomite

I thought I had the rarest. New water pump. Fired it up and went for a drive....impeller spun free of input shaft on new water pump. I caught the temps before they got into red zone.

I've had 2 in unopened box NOS pumps do this....only pulleys spun off shaft.

[tccrab]

Originally Posted by c4koh

A "bad" injector (concluding it's bad from the off-par resistance) still functions, just badly, right? And perhaps in my Secondary #2 (resistance at 0.7 ohms) it's just shot?
When they're "shot" - do they let in any fuel (as basically drips rather than nice injected spray) or do they simply clog up and not allow anything.

Still unsure why the car drives fine and powerfully until it's at least warm, and seemingly with no problems (and very, very fast) with POWER KEY on.

Thanks all so far for the help. Will report back once I've replaced the injectors.

The coil in the injector opens and closes the pintel which controls the flow of the spray. If the pintle doesn't open all the way the spray pattern gets erratic (think of your sprinklers in your front yard).
A bad injector can spray badly or drip fuel or in the worst case do not work at all.
As to why your motor runs worse when it's warm, that's quite simple. Resistance and temperature share an inverse relationship.
As temperature goes up, resistance goes down and a marginal injector becomes a non-working injector.

As far as injectors, unless your budget demands otherwise, go with new injectors. I've had great luck with Accells, FIC sells new ones, and at the top of the price spectrum is RC Engineering, but by all accounts they are the best.

Of course, Jerry more than likely has everything you need in stock and I'll bet that if you send him an email today you will have the parts early next week.

Good luck!!!

'Crabs

[Franke]

Gold Cylon and Tccrab is right on. Replace the injectors ASAP. My car had 1 bad primary and 3 bad secondary injectors and it ran good cold but only until I got on it did I realize the lack of power in the secondaries. I had and you will have a slight miss at idle with the bad primary injector when the engine is hot but probably not when it is cold as the coils in the injectors regain some of their resistance cold. Saw it for my self with a hot then cold injector test. When the injectors short out (drop in resistance) they do not provide the fuel needed for the present engine condition. I had a friend with a 91 L98 that ran great for about 45 minutes and completely quit until it cooled down again then it would start and run fine for a short bit and repeat. He had 5 injectors that were bad. WE replaced all 8 of them and he said it was like a new car.

[PhillipsLT5]

Originally Posted by XfireZ51

Ask Pete what happens when your motor heats up to 261.

http://zr1specialist.com/HAT%20Web/p...d%20gasket.htm

[Kevin]

looks like what injectors were when I replaced them the first time. All of yours need to be redone, fuel injector connection is who you need to call

[c4koh]

Originally Posted by tccrab

The coil in the injector opens and closes the pintel which controls the flow of the spray. If the pintle doesn't open all the way the spray pattern gets erratic (think of your sprinklers in your front yard).
A bad injector can spray badly or drip fuel or in the worst case do not work at all.
As to why your motor runs worse when it's warm, that's quite simple. Resistance and temperature share an inverse relationship.
As temperature goes up, resistance goes down and a marginal injector becomes a non-working injector.

Great - I read up on them (fuel injectors) , and I see now how they work. The magnetic field induced moves the pintle by the electric current passed to the solenoid wiring/coils. So, presumably a fresh/good coil has a good winding, and reasonable resistance. As it gets gunked up, the coil works worse, likely touching each other providing parallel resistance paths (and hence reducing overall resistance) and so on.

Will read up about which injectors to get for my budget (noting already the ethanol-averse stock and rebuilt ones, so not going for those), and also what else to do while under the plenum. I've removed the plenum on my old ZR1 (when back in England) and re-used the gasket the first time, but put on the new gasket the second time. It's been 7 years since I last removed the plenum, but it was easy enough with the right instructions, patience, and digital camera to record everything I removed... to remind me what to put back...

Thanks again all for their help.

[Kevin]

Stay away from the rebuilta