Sorry to be Redundent - Help

[bhermes]

I have posted a few times in the past about this issue and have read some other posts but I have gotten myself a little confused on where to go first.

I will do the best I can describing the problem/issue or opportunity. Remember I am not a mechanic but tyring to learn.

I drove the car really for the first time in almost a year after dropping my gas tank, getting out rust, coating and reinstalling. The Fuel Filter was also replaced.

Here we go...........

Drove car about 50 miles, some at 30mph, some at 80 mph, and some in stop and go traffic. Car starts up fine, first try no issues. Idles at about 900-1000 rpms. Car ran ok for the majority of the trip. I feel it was a little sluggish off the start and while pushing on the gas at upper speeds (50-80) the car will push back some when letting off the gas pedal. It also revs up about 500 rpms when coming to a stop. But in general the car ran ok. The issue is that 3 times during the trip and I beleive at speeds over 50 mph the car acted like it was running out of gas. It wanted to stop for about 2-3 seconds and then took off again. After the last event of this happening the car drove about 8 miles ok and I was home. It never did completely die.

I suspected previously that the rust in the tank was causing the problem but that has been corrected.

Could it be injection problems? Again only happened 3 times for a few seconds during a 90 minute drive.

Thanks in advance for some initial guidance. I would really love to find someone in my area, KY to drive the car that knows what things should feel like but have been unable to find anyone.

[siteunseen]

Revving up 500rpms at a stop is the BCDD. It has a nut on the bottom side, turn it counterclockwise 1/2 turn and drive, if that doesn't get it to fall back soon enough try another 1/2 turn. My opinion on the other running out of gas feeling is based on my experience with my '77. I dropped the tank and cleaned it as well but the problem was still there, it ran like crap up until 2500rpm and after that it would run strong. A mechanic kept it for about a month and told me the on ly thing he could figure out after doing a full tune up was low fuel pressure. He partily clamped off the return to tank line and raised the pressure that way and said it ran better but still not perfect. I got it back and went to Radio Shack and spent $5 and 30 minutes doing this, http://atlanticz.ca/zclub/techtips/tempsensorpot/index.html, it runs sooo good now I've started spending money on it again, wheels and tires and a new stereo. Carpet and seats are next then a paint job.

[siteunseen]

BCDD is under the throttle body, http://www.classiczcars.com/forums/fuel-injection-s30/45792-bcdd-rebuild-parts.html, post #7 has the pictures.

[Zed Head]

the car acted like it was running out of gas. It wanted to stop for about 2-3 seconds and then took off again. After the last event of this happening the car drove about 8 miles ok and I was home. It never did completely die.

I remember some of your posts but can't remember the details of your engine. Is it stock? Have you modified anything like the ignition system? When you say it feels like it's running out of gas do you mean a complete loss of power or a sputtering and coughing feeling?

[bhermes]

Car is stock. The only thing really changed is an upgrade in the alternator. I also had to replace the ignition switch and had a few issues with the plug under the steering wheel but i think corrected. As far as anything else should be stock.

I am not sure if I am loosing power but feels a little worse than sputtering and coughing. If I am actually loosing power what is the easiest way to tell? RPM gauge? My dash lights do not work, probably when I was getting 18 plus volts to the battery, and it was dark out during the trip.

I will check out the BCDD tonight, I remember some discussions about this before.

Thanks.

[Zed Head]

One good clue would be the tachometer behavior. If the ignition module, or coil, or power to the ignition system, is going bad the tachometer needle will probably jump around or just go to zero. When mine was going bad the engine would still run but poorly and the tachometer needle was jumpy and read about 1.5 times actual engine RPM.

You'll need to have a general feel for what RPM should be for your speed and gear. For example, mine showed that I should have been going about 80 mph, when I was only going 50. Mine also would fix it itself if I turned the engine off and restarted. They become more heat sensitive when they're failing and higher RPM generates more heat.

If it's a fuel problem the tachometer will probably be fine when you're in gear because car speed will dictate engine speed. Assuming you have a stick shift.

[bhermes]

OK. I have a 4 speed manual. A little confused on how I am to know what rpms should be at a given mph? Bare with me not a mechanic. Trying to learn. Is there a curve somewhere. When you said yours should have been going 80 mph are you refering this based on the rpm readings? During the normal periods the rpm and mph gauges are consistant.

When you said jump around or go to zero do you mean during the problem periods or all the time. What I am trying to get at is if this is the problem would it be this random or more consistantly showing issues.

Sorry, just hang in there and I will get it.

I really need to look at gauges when the issue occurs but damn if I always forget. Just fighting to keep car from stalling and then after a few seconds she is off and running again.

[EuroDat]

Revving up 500rpms at a stop is the BCDD. It has a nut on the bottom side, turn it counterclockwise 1/2 turn and drive, if that doesn't get it to fall back soon enough try another 1/2 turn. My opinion on the other running out of gas feeling is based on my experience with my '77. I dropped the tank and cleaned it as well but the problem was still there, it ran like crap up until 2500rpm and after that it would run strong. A mechanic kept it for about a month and told me the on ly thing he could figure out after doing a full tune up was low fuel pressure. He partily clamped off the return to tank line and raised the pressure that way and said it ran better but still not perfect. I got it back and went to Radio Shack and spent $5 and 30 minutes doing this, http://atlanticz.ca/zclub/techtips/tempsensorpot/index.html, it runs sooo good now I've started spending money on it again, wheels and tires and a new stereo. Carpet and seats are next then a paint job.

I second the Thermo time mod. It really improved the divebility of my 77 280Z and it had similar hestitations like your describing. I didnt get it adjusted using a dyno test bank. Simply ran the wiring inside the cabin so I could play with it and kept adjusting it between fuel tank fills. Try to get a balance between power and economy. Them moved the resistor back pemanently in the injector wiring harness.

Chas

[bhermes]

I am going to mess with the BCDD this weekend and see if I can dial out the 500 rpm additional rev during stopping.

Secondly, I would like to add the 1k linear pot but I am not sure I am completley understanding the photos.

I see 2 Thermo time wires, 2 water temp sensor wires, and 1 temp gage wire. Can someone attempt in words where the 2 pot wires go and what happens to the rest of the wires mentioned. I would like to do this over the weekend as well and make the simple crude tweaks. Not sure if I am good enough to make this wiring change. I guess I did successfully make the simple wiring change for the upgraded alternator so maybe I can. Who knows but willing to try.

I am always amazed at the knowledge of the people on this site. It is truley a gift to those of us just starting to learn. One day I hope to be able to help others.

Thanks in advance.

[bhermes]

One other thing I would like to do is add some Lucas Fuel Injector Cleaner to my gas. Just looking for a few comments on whether this might help clear up some of my problems or if it may cause more. I saw a post about a possible problem someone had after adding the cleaner.

Thanks.

[FastWoman]

The loss of power under load sounds like a fuel starvation problem to me. If your pump is like mine, it will fail slowly, not catastrophically -- a bit like congestive heart failure. Pull off the return line, and attach a hose that runs to a gas can. Then run the pump. (You can jumper the appropriate wires on the fuel pump relay connector.) Observe the return flow: It should be healthy. Keep running the pump for 15 or 20 min, giving the pump enough time to heat up. Again, if your pump is anything like my old pump was, the return flow will get more and more meager and then will stop, as pressure sags below the 36.3 PSI.

My old pump would get me out onto the interstate and then would leave my engine sputtering until it failed and left me on the side of the road. When it cooled off, it would pump again.

I, too, can recommend the coolant temp sensor resistance tweak. It solved the lean-running issues in my engine. Mine is a '78, and I think this lean-running issue plagues '77/'78 (particularly '78) ECUs. The ECUs are analog, not digital, and they are prone to calibration drift (towards shorter pulses, resulting in less fuel delivery) as the semiconductors age and break down. For all I know, the '77/'78 ECUs might be completely different from the '75/'76. I know they started with Bosch ECUs in '75 and ended up with Hitachi in '78, but I don't know where the changeover was made.

[siteunseen]

My '72 has a 4 speed and if I recall right I believe 3,000 RPM is about 70 MPH, 3800 to 4000 is around 80, I THINK! The 2 wires off the Pot go in between the coolant temp wires, don't mess with the Thermotine wires or the temp gauge wire. You'll have to buy the blue crimp electrical connectors, 1 female and 1 male, you can get a pack with them both at Radio Shack too I believe. And do what Chas says and run it inside with you through one of the holes on the drivers side fire wall, speaker wire worked for me. When you figure out if that helps then put it back out under the hood like in Blues pictures. I am going to buy a more precise one like Fastwoman uses, she has one that you turn with a small screwdriver- little bits at a time. The ones at Radio Shack are like volume knobs and can get out of adjust when you forget which way to turn it, after a few beers is when it happens to me.