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Occassional Engine Stutter - '77 280Z


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Hello again!

 

I thought I would start another thread about my '77 280Z and it's engine issues. A little background on me:

 

I have done minor repairs such as replacing brakes, tuning an old carburetor, and even pulling a few pistons from an old '55 Plymouth. But I am pretty ignorant when it comes to the inner workings of a car, for the most part, though I am willing to learn.

 

Now, a little about what's going on with the Z and what's been done thus far:

 

When I first got the car a few months back, the car would not run at all. I could get it to start some of the time, but could not keep it running. It would sputter and spurt and then die. Even when it seemed it was somewhat running, applying the gas would cause it to just quit.

 

The car was then worked on by a mechanic and he did much to the vehicle for me - went through and replaced all the fuel lines, installed a new fuel pump and filter, replaced the injectors and pig tails, checked fuel pressure, etc. I had known this mechanic for some time and trusted him, but it turns out he is really good with newer cars (i.e. cars where a computer can tell you exactly what is wrong), but was frustrated with my Z and trying to get it to run smoothly. I got the car back from him mostly running, but it would stall ... a lot. In other words, I could drive the car and it would end up stalling at odd times. It was not heat related as the engine was sufficiently cooled by the radiator, etc., and maintained a good engine temp throughout. The car would purr along ... and then die. Sometimes it would die shortly after starting it and driving. Sometimes it would go for quite some time (15-20 minutes of constant driving) and then it would start to sputter and lose speed, going to a crawl and then shutting off.

 

When the car stalled out, turning the key would not get the engine to run. It would crank, sputter again, and the die. Sometimes it would just crank and do nothing more. If I let the car sit for a few minutes (literally a few minutes ... sometimes only 5) and crank it, the car would start up and drive as if nothing were ever wrong.

 

Since the mechanic did not want to deal with the car any more, I decided to see what ignorant me could do. I purchased and installed an inline fuel filter and installed it between the tank and the fuel pump. I thought that perhaps there was rust in the tank. At least with the clear plastic filter I could check it and see what was going on. The filter seemed to help and the car did not stall for a few days, but then it started to stall again. Looking at the filter there was water in the gas and very little rust at all. I used a bottle of HEET and this seemed to help, but not completely. The car would sputter from time to time, but not always stall out. I fueled up and tried a second round of HEET and the car was running awesomely after this ... for the most part.

 

The car no longer stalls and shuts down. But there are a few times where it starts to stutter. Most of the time it does not lose speed, but just sort of stutters. You can hear that the engine is not running as smoothly and you can feel it as you are driving. This has happened both when I am driving in the city (i.e. 35 MPH) and on the highway (65 MPH). Tonight, however, as I was driving on the highway, it started to stutter and lose speed. It did not die out (dropped from about 60 MPH to about 50 MPH and would not go any faster) and after about 30 seconds of driving that way it righted itself and purred along just fine all the way home.

 

I need to check the filter to see what's going on, but it's dark right now. I'll do this in the morning. But since this is on my mind, I wanted to share what I am currently experiencing to see if anyone thinks they have an idea what is going on.

Could something like the ECU or Ignition Control Module be failing or starting to fail (and, if so, could either of these have this kind of effect)? If this were happening to your Z, what would you check first?

Please keep in mind that I am fairly dumb about this stuff, though learning. Please spell out things like "AFM" as "Air Flow Module" since I will most likely not know what you are talking about. When I first saw ECU, ICM, and the like, I had to do a search to find out what they were and hope that I was finding the right thing. ;)

 

Thanks again for any help and your patience. I truly appreciate it.

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I had an issue similar to this when my fuel pump was going bad, except kind of the opposite order. It started doing it once every couple weeks on the freeway for a few seconds and then eventually it wouldn't run for more than a few minutes without it crapping out on me.

 

Since it sounds like you have some gas tank rust issues, I would suggest draining the gas tank and dropping it out to take a look at it, or at least looking in with a flashlight. It's a well-documented problem with these cars.

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Does the car stutter if you leave it idling? Or do you have to be driving it?

 

Is it stuttering or rattling or misfiring? It really would be nice to get a nice landscape video of the problem if you can manage safely.

 

Well the 4 things a car needs is air, fuel, spark, compression. For an engine to stutter one of the four things is off balance.

 

Fuel, the clear fuel filter is a good indicator another nice indicator would be a fuel pressure gauge. A sudden drop in fuel pressure could cause the car to stutter or miss. This is caused by a few things. A leak or crack in the fuel line, a clogged fuel pump filter, a dying fuel pump, varnish in the fuel lines, rust in the fuel lines, clogged injectors etc. The car stalling and not starting up after a while could indicate a rich condition. 

 

Air, a less likely culprit, but insufficient air can also cause a car to stutter and die. The fact it is running points towards this not being much of a problem.

 

Compression, also not a likely culprit as the car is running.

 

Spark, it doesn't seem like you have done any work with the spark. An intermittent stutter and a car being able to start backup after a while points towards a weak coil or spark. Taking out the spark plugs and taking a picture of them in a row would be really useful information. Also the voltage of the car when the car stutters, when the car is running, and when the car is off would be also helpful. 

 

If everything checks out, then the culprit would seem to lie in the old electrical connections or the ECM. That can be quite an ordeal, so I would check the easier tasks first.

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Thanks, seatlejester. I will try to respond to each point with what I know.
 

 

Is it stuttering or rattling or misfiring?

 

While it has misfired once that I am aware of, the car stutters when it loses speed. It sounds and behaves like a car running out of fuel.

 

 

Fuel, the clear fuel filter is a good indicator another nice indicator would be a fuel pressure gauge. A sudden drop in fuel pressure could cause the car to stutter or miss. This is caused by a few things. A leak or crack in the fuel line, a clogged fuel pump filter, a dying fuel pump, varnish in the fuel lines, rust in the fuel lines, clogged injectors etc. The car stalling and not starting up after a while could indicate a rich condition.

 

The vehicle has had all new fuel lines installed, a new fuel pump (the one in the engine compartment), new injectors and new pig tails. So, I don't think it is anything in the actual lines (i.e. varnish in the lines). But there is a small amount if rust in the inline filter. Once the ground is dry I am going to swap out that filter for another one (I keep a spare in the car).

 

 

Spark, it doesn't seem like you have done any work with the spark. An intermittent stutter and a car being able to start backup after a while points towards a weak coil or spark. Taking out the spark plugs and taking a picture of them in a row would be really useful information. Also the voltage of the car when the car stutters, when the car is running, and when the car is off would be also helpful.

 

The vehicle has all new spark plugs. I've not tested the coil. The volt meter on the dash is staying consistent (about 15) when these episodes happen, from what I recall, though I will pay more attention the next time it happens.

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Interesting - I used to own a '55 Plymouth 4-dr Belvedere with a 273 V-8 and an automatic. Pretty much didn't like that car.

 

Seattlejester gave you some really good advice. Really sounds like you have a contaminated fuel tank to me. You never mentioned the mechanic pulling it and checking it out.

 

One thing that doesn't sound right, though. The fuel pump on a '77 280Z should be mounted in the rear wheel well area on the passenger side - not in the engine compartment. Those pumps like to push, not pull. If the pump is trying to suck the fuel any significant distance it won't work properly.

 

Also, your issue sounds like you may have some vapor lock going on. The 280Z had a problem with that. The heat shield between the exhaust manifold and the fuel rail didn't quite get the job done. When that happens the car won't start a couple minutes after shutting it down but will about 15 minutes later. Sometimes it will stutter a little as it starts up but then will run ok. It will not occur as long as the engine is running.

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One thing that doesn't sound right, though. The fuel pump on a '77 280Z should be mounted in the rear wheel well area on the passenger side - not in the engine compartment. Those pumps like to push, not pull. If the pump is trying to suck the fuel any significant distance it won't work properly.

 

Sorry. That was my mistake. I meant FUEL FILTER not pump. The fuel pump is indeed in the rear wheel well.

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Along the same lines as phantom, I think I see a problem right there.

 

If you have rust in the inline fuel filter in the engine bay, then that means you probably have rust getting past your pump. Your pump depending on make/model/style should have a pre-filter in front of it. If rust has made it all the way to the engine bay in the fuel lines, then either you don't have a pre-pump filter, or the pump filter has failed and your fuel pump is eating rust. Depending on what style the pump is that could mean the pump is taking extra amperage or the internal teeth are all chewed up, once it gets to a certain point the fuel pressure can drop with either situation. 

 

Vaporlock is also a good point, but if that was the case I imagine just idling for a while, turning the car off and starting it back up should yield the failure to start problem. That would also be a good check. Where abouts are you located? Is it pretty hot when it fails to start?

 

A fuel pressure gauge would help us out, AFR would be useful. Part number for the fuel pump is also a good piece, and the presence and condition of the pre pump filter would be all good pieces of information. Draining the fuel tank would also help us out with the condition. If rust flakes fall out in a decent number then the culprit highly points towards 

 

If the spark plug has been swapped then if the order is wrong it could cause a stutter not to mention make the engine run pretty poorly. Just do us a favor and double check, I believe it is 153624 going clockwise.

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Hi Seattlejester,

 

I had mistyped earlier. The rust is not in the fuel filter in the engine compartment. That is a metal fuel filter and I cannot see what is in it. What I had meant was there is a small amount of rust flakes in the inline fuel filter that I installed between the gas tank and the fuel pump (the fuel pump is in the rear wheel well, as it should be). This inline fuel filter is of the clear, plastic type, so I can see what is in it.

 

The spark plugs were replaced by a mechanic and the distributor checked. When the car is running, which is most of the time, it runs very smoothly. In fact, I had taken it out on the highway and, when no one was around, ran her up to 100MPG with no issues ... the Z still wanted to pull with no issues. It purred along smoothly as all get out. No shaking. No stutters. So, I don't think there is an issue with the spark plugs being swapped, etc.

 

When I get a chance to install a pressure gauge and to crawl under the vehicle to check the fuel pump part number, I'll let you guys know what they say.

 

I live in Virginia. It has been both cool and warm (near 90). Today has been very cool ... low 60s and overcast. I took the car out and it ran fine, then stuttered and stalled. The car would not restart, but stammered. I waited about a minute and the car fired right up and ran the rest of the way home with no issues. This is the same behavior it can have on a very hot day, so it does not seem to be temperature related.

 

If I run the car at idle for a while, shut it off and then start it back up again, it starts up just fine. No issues here. The only time starting the car is an issue is if it stutters and stalls out. Then it just needs to sit for a moment and then it starts just like there were no issues. To me, this seems like something is interfering (rust or water) and letting it sit for a moment allows whatever it is to settle to the bottom or move on, etc.

 

I plan to run through this tank of gas, fill it up, and apply some more Heet and see where that takes me. If I get a chance (whether permitting before things get too hectic here), I will try to drop the tank (before filling it up) and see what we have. I've never done this before (dropped a tank), so this should be a bit of an adventure. ;)

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I would drop the tank and take it to be cleaned and sealed.

If you are getting visible rust in that filter you're putting off something that needs to be addressed.

Good time to paint it afterwards.

 

This is a great time for you to learn more about your car, the more you can learn the better off you will be.

 

People today don't know these cars. The great thing is that they are simple, but it takes time, and you have to be methodical and check everything and address one thing at a time. There is usually not a quick fix on a 30+ year old car, there are things that need to addressed along the way - count on it.

 

Get a datsun service manual or a PDF of it, this will help you learn.

 

This forum has a lot of people with a lot of great knowledge.

 

When you buy an old Z it is a project, a journey.

 

If you're looking for a low maintenance daily driver you'll be frustrated and disappointed unless it has all been gone thru and addressed, and it probably hasn't.

 

But the journey is the fun of it!

 

Enjoy-

Steve

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Hello steve edrington. Thanks for your help and advice. I appreciate it.

 

Yep, I need to get the tank cleaned and sealed. It's next on my list (next to finding someone local that can/will do the work! They seem to be getting rarer ... at least in my area).

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Check for true radiator repair businesses, I think they will be a good bet to fix this or will know where to get it fixed. 

 

- Steve

 

I have. None of them in my area (Roanoke, VA) do the work any longer. I either will have to do the work myself, send the tank out to a place that still does it, or get a new tank. I think I will opt for the first option. There seems to be plenty of tutorials on how to do this.

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