Checked spark- yellow not blue - is this normal?

[Bob95065]

Ia m working on a 1990 RRC. This is my first LR experience.

I checked the spark by pulling a wire and putting a new spark plug on the end. I held it to ground and started the engine. The spark looked yellow to me which wasn't blue liek I expected.

Is this normal? SHoudl I replace my coil or amplifier?

TIA,

Bob

[jagfixer]

And we are checking spark why?

[Bob95065]

I am getting cylinder misfires on both banks and terrible gas mileage with black plugs. I suspected weak spark so I checked it.

I have checked spark before on other vehicles and had blue spark. Should my spark be blue or iss the yellow spark normal? In other vehicles yellow spark was an indiaction of a problem with ignition.

[pvillese]

When I was working on my ignition my spark was blue. If your plugs are black I'd say you need a tune up. Beware, when I did my tune up the rotor(an ome replacement not from LR) I got was bad and I spent months trying to find why it was running ruff and the new rotor ended up being bad.

[Bob95065]

When I was working on my ignition my spark was blue. If your plugs are black I'd say you need a tune up. Beware, when I did my tune up the rotor(an oem replacement not from LR) I got was bad and I spent months trying to find why it was running ruff and the new rotor ended up being bad.

I just put in brand new plugs and they fouled really fast. My MAF wasn't functioning and after a good cleaning with contact cleaner it appears to be functioning. Before I could disconnect the MAF connector while the engine was running and there would be no change in the idle and no CEL. Now I disconnect the MAF with the engine running and the engine immediately dies and I get a MAF code.

I found out about using aftermarket rotors the hard way and am running a genuine Lucas. I also replaced the cap, wires and plugs while I was at it. I tested the spark with a brand new plug not one of the black ones.

This vehicle was given to a friend by another guy. The truck sat for years and I am resurrecting it for him. I have changed all the fluids and filters and now I think I am hunting down the problem that got the truck parked in the first place.

I have a bad vacuum advance (diaphragm is rotted) that explains no power and a vacuum leak. I am going to the junkyard tomorrow in search of a distributor with a good advance unit. I think I may look for a coil and a spare MAF sensor just in case.

If I had a bad spark amplifier would that cause yellow spark? if the amplifier was bad would I have spark at all? Could this be the coil?

Bob

[Disco Mike]

How about that 19 year old coil, if it is the problem, I would up-grade to a stronger aftermarket coil.

[pvillese]

I'd agree with Mike, I would toss on a MSD blaster coil, should be in stock at your local parts store, cheaper than original replacement and more powerful. Obviously you need to fix the advance but that shouldn't cause you to get a yellow spark. I think if the amplifier/ICM is bad you wouldn't have spark or at least not all the time if it is going, if you want to make sure O'riely will test it for free and since you are probably going to have the distributor out I would test it then, it is a pain to get out when the destributor is in the truck. Oh, I see you guys don't have O'rielly stores in CA, I'd check if another parts store can test it for you.

If the amplifier is bad, you have a few options, I've seen people wire MSD 6 boxes directly to what was the inputs to the amplifier, or there is a guy that sells a custom designed amplifier/ICM and coil package for a not too bad price. There is also a guy I believe in Maine that sells the amplifiers for a decent price, or I'm sure you could get a used one from someone on this forum. I know there are links to all this on threads here, if you need a specific link I probably have it saved somewhere.

[Bob95065]

I got a junkyard distributor, coiil and MAF yesterday and put them in. The donor vehicle was a 1988 (I am working on a 1990) and I found out the distibutor caps were different (taller) in 1988 so I stripped the amplifier and vac advance and put them on the original distributor. I also replaced the coil with the Lucas I bought at the junkyard.

I had better acceleration with the "new" igition but I noticed missing over 2250 RPM. This morning I put the original Bosch coil in and the missing stopped. I had a a bad feeling when I put the Lucas coil in (I have a history with the prince of darkness - I have a 1964 BSA motorcycle I am restoring.

I have come to the conclusion that this is RRC is an excellent candidate for a MSD ignition. I had a 6C box and Blaster 2 on my Toyota truck with the dog slow 3.0l V6. I got more power and 2 MPG with the MSD ignition.

BTW now my temperature gauge doesn't work. Any ideas on how to diagnose the sensor?

Thanks fo rthe help, Bob

[pvillese]

If you the temp gauge is staying at zero its probably the wiring. Mine is that way, I replaced part of the wire but it is not completely fixed but if I play with the wire especailly the part close to the battery it ussually works. I was told if the sensor is going you get goofy readings not just no reading.

I put an MSD 5 box and blaster 2 coil on my RRC and it starts a bit better and I had a hesitation before the instalation of the MSD 5 box that feels to have gone away. I'm not sure of the gas mileage improvement but it seems to have improved. If you do put a box on make sure you get a tach adapter, maybe the tach output on some of the 6 boxes will do but with the 5 box the input signal is not strong enough to signal the computer and the MSD box.

[Bob95065]

I am very embarrassed to say I looked under the hood and the wire was off the temp sensor. I reconnected it and id the gauge works fine.

Bob