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bhermes

Last try on this issue

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OK, I have posted on this issue a few times and thought I would start one last thread.

I have my 76 in the shop and trying to give the mechanic some suggestions based on your input. I hated to take it to him but I needed a little better look than I was capable of giving the car.

Just about every other time I drive the car,which has not been very often (10 times in a year), it stops on me. I initially thought it was a gas delivery problem; however, after installing a pressure gauge, I believe it is more likely loosing spark. A couple days ago I went for a 30 mile drive and after about 28 miles the car shut down. The pressure gauge was reading 33-34 psi. It would not restart. Waited about 10-15 minutes and the car started right up and I drove the last 2 miles no issues.

Where should I look first. A few suggestions to look at would be nice. Is there any chance that the TPS could be the issue? Is it at all temperature sensitive.

Help.

Thanks for the one last look.

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It is probably the ignition module overheating. You can replace it or get a distributor from a 280zx (that has a better ignition module on the side of the distributor)

It could also be a condenser (capacitor) shorting due to heat.

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Thanks Blue.

Forward to mechanic and will see. I assume my mechanic will know how to check but is there a good way to tell if either of these are bad?

Again, thanks.

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Use a can of dusting air. When the car has trouble running/starting, hold the can upside down and spray the Transistor Ignition Unit. That will cool it down quickly.

Also, you can replace the TIU with a GM HEI unit. I think Chas, aka Eurodat, has a thread where he was mounting the HEI inside the TIU.

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Sometimes the tachometer will give a clue. If you're in gear, engine turning, and power disappears but the tachometer still shows the engine turning that would mean you still have spark. If the tachometer drops to zero immediately but you're still coasting in gear with a dead motor, no spark, maybe the module, or the coil, or power to either/both. If the tachometer starts jumping around or reads abnormally high or low, it might be the module. Not a 100% clue about the module, but might tell something.

Forgot one thing, that I just recently figured out on my car. One of the PO's of my car had jumped the two pickup coil wires together at the junction box. I never really figured out why until the other day when I was testing old parts to see if they were any good. One of the two pickup coils from that distributor, long since swapped for a better one, was bad. The jumper wire allowed the ignition module to see both pickup coils and use the one that provided a good signal.

Short story - maybe one of your pickup coils is bad. If so, the engine would only run when cold.

Edited by Zed Head

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So when it does die on you do you immediately check for spark? It would take a second with a screw driver or something to jump the spark plug wire.

Sures sounds like ignition

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You could be having a similar problem to what I was having. Mine didn't stop when it warmed up, but I wouldn't call it drivable either. It barley made it home in 1st & 2nd gear.

The problem I had passed all the FSM test "I could do" when it was cold. It wasn't predictable, sometimes after 5 minutes of driving and other times after 30minutes. If I pulled over on the side of the road it would idle and rev ok, but once it was under load it would start playing up again.

It might sound strange, but you do have some luck on your side. If its stopping all together something has temporarly failed and that should be easier to find.

Here is the thread explaining my efforts with the HEI module. It wouldn't be hard to install a tempory unit next to the coil to isolate the TIU.

http://www.classiczcars.com/forums/electrical-s30/52621-fitting-hei-module-transistor-ignition-unit-1977-280z.html

Good luck hunting it down.

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SteveJ/EiroDat, checking into the TIU and HEI situation. Also, I really had not noticed it being consistent; however, not enough data. I initially did not think it was temperature related but the last several times I took short drives, 15 miles or so no issues and the first time I drove about 30 miles the issue happened again. Mechanic drove several short drives and one 30+ mile drive with no issues yet.

Zed Head, the odd thing is that the RPM's did not immediately drop. Need to really check again when it dies.

MadKaw, I have not immediately checked for spark. The mechanic is waiting for it to fail on him and will do so when it does. Like always he has driven some and the car is acting ok. It will fail on him soon I am sure.

I have spent all my time chasing a fuel delivery issue and the mechanic is convinced it is spark.

I think I have some good areas to start attacking and just waiting for car to fail on mechanic to determine what he sees.

Thanks.

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I had a situation like this working on a coworkers car. After doing everything -----including pulling the gas tank, I gave up. Someone else had found that this girls car had mice in there chewing her wires. Car would run and then quit for no apparent reason. I guess it was a wire giving out after being loaded for a while driving- maybe a ground, not sure.

My guess is module or wire issue.

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I had been experiencing the exact same scenario, I changed the TIU, Coil, Plugs, Wires, Cap. Tested everything and still could not figure it out. Suspecting a Vapor Lock issue on the rail, I decided to go to the newer aluminum fuel rail setup and reduce/eliminate vapor lock as a variable. While doing all of this and installing new injectors, I discovered that my #1 injector had failed - but that would not have killed the engine just made it lope. While changing the fuel filter, I noticed that it had come apart internally (see other thread) and so what I believe I was facing was a combination of intermittent fuel blockage which caused a vapor lock. This may not be your issue, but it is damn similar, especially if you have checked for spark and looked over everything else. So you might want to replace the fuel filter (buy a good one) and see if that doesn't change things. Please post what you find out....

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If it is fuel delivery would I be getting 35 psi at my fuel gauge? I get a little confused with pressure vs flow.

This is the reason I was leaning more towards spark than fuel.

Thanks.

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If it is fuel delivery would I be getting 35 psi at my fuel gauge? I get a little confused with pressure vs flow.

This is the reason I was leaning more towards spark than fuel.

Thanks.

If there were a blockage, I am thinking that you would have ~35 psi on one side of the blockage and lower pressure on the other - especially when there is demand from the fuel system. What you could do is place a pressure gauge inline under the hood to keep tabs on the pressure. At the same time, keep a timing light in the car. When there is a engine stall, you can immediately check the fuel pressure reading and crank to check for a spark. You should be able get some results that could take you in a more definative direction for troubleshooting.

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Mechanic has been driving the car for about 4 days now and it has not acted up. Still waiting so he can check both fuel pressure/flow and spark.

I told him today to just drive it all day until it breaks down.

I will update when it fails and what he finds.

Again thanks for all the advice.

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Subscribed, I'm in the same boat. Car will drive perfect, die on me, wait 10-15 mins, then I can drive home. I'm going to look into the ZX distributor.

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Ok, sorry so long to post again. According to mechanic wires to temp sensor we're loose. He drove car about 45 mile one way trip twice with no issues. Normally car would have a problem with this length of drive. Need a little more driving to be sure. Any thoughts if this makes sense? Heating up during driving?

I will keep everyone posted

Thanks

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I have seen this before as well as a loose wire in the low voltage harness from the coil area to the distributor that stopped the spark.

The wind from the road and from the fan will shake these wires strung across from the fender to the engine. As well wet spray from the road will hit them (and the electrical connectors).

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I guess what I was wondering is if the car heating up while running, shutting down, waiting 15 minutes, and then restarting could be caused by a loose temp sensor. What happens when the temp sensor is not connected or a loose connection. Current flow issue or arcing.

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From Blue's Tech Tips, "It should be easy to see that the resistance decreases as the engine warms up. It is also worth noting that the FSM says the amount of fuel injected decreases as the engine warms up." http://atlanticz.ca/zclub/techtips/tempsensorpot/index.html

If they were loosely getting contact, air from the fan as Blue said, it would do what your's has been doing. Clean them, put dialectic grease on them and crimp them together tight. Take your phone along for an hour drive around the neighborhood.

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I'm new to Datsuns, but I've seen something similar on Hondas. Usually it's a main relay. Especially if all the timing components are good/new/within spec. Please don't lash me for thinking out loud. Hope it helps, if not at least one less thing to worry about.

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Got the z back on Friday. Drove about 50 miles with no issues. Car drove great. Other than my windshield wiper flying off during a rain storm. I drove about 50 miles over the weekend and again no issues. The car seems to be good but still need a little more drive time.

I will post again soon.

My students at school are starting to install a new amp, sub, and speakers. Living dangerously but I think they can do it.

Thanks for all the help and suggestions and I will check back soon.

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One thing. I now have dash lights so driving in the dark. The head lights seem a little weak. Any thoughts. Maybe an upgrade.

I have upgraded the alternator not sure if this helps.

Thanks.

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$350. Is there not a better bulb I can just use. Sorry. Probably showing my ignorance. Is the bulb easy to replace. I can probably figure tis out on my own.

Thanks.

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