Redwing's Car - An Update

[SteveJ]

Round two for the 280Z.

 

I filled up the back of my wife's station wagon and drove over to Jai's house.

 

I put in the battery hold down bracket I fabricated (and my wonderful wife painted). No more twine holding the battery in place. Those are M6 wing nuts holding the two parts of the bracket together. I figure that if a wrench is needed to get it apart, make it a 10mm.

 

Then I put fuel pressure gauge in downstream of the fuel filter. (Thanks Cliff!) There was no pressure in the line when I removed it to splice in the pressure gauge.

 

The car started up and idled fine. The pressure was around 30 PSI. Around the time the thermostat should open, the pressure went up to around 34 to 36 PSI, and it ran rough. I checked the block temperature with an infrared thermometer, and it was around 180 to 190.

 

After a few minutes, the engine smoothed out again, and the pressure was back to 30. It went through this cycle a couple of more times. During the last time, we tried to give the car some gas, and the engine stalled. The fuel pressure dropped rapidly.

 

We tried to restart the car. The fuel pressure went back up, but it didn't fire. I put an inline spark checker on #2, but it looked a little weak. The fuel pressure dropped slowly after cranking, taking about a minute to drop to 0.

 

Thanks to Jonathan Russell, we had a set of plugs, plug wires and a cap. I pulled #2 first. It was black and looked a little wet. It was a couple of minutes before I pulled the other plugs, and with the hot engine, I am thinking they might have had time to allow gas to evaporate. Number 6 is the rusty plug.

 

I talked to a friend and all-around Mensch, Tim McGovern, who advised me on how to adjust the AFM. I first thought the spring needed more tension. I adjusted it, and didn't like the results. I adjusted the spring to have less tension, but the screw that holds the cog in place would not tighten sufficiently. I took the screw out a couple of times, trying to get it to seat, and then it happened. The rectangular piece that locks into the cog's teeth fell off...into the gravel below. I uttered the appropriate cuss words and felt about two inches tall. Jai tried to search for the proverbial needle in the haystack, but she wasn't having much luck. We pushed the car back and searched some more. I thought I'd give my hand at fabricating a replacement, so Jai produced an old colander. I used my wire cutters and snipped off one of the feet. Zing! It also disappeared into the gravel. I managed to catch the second one I snipped off. I grabbed my metric bits and drill and drilled the correct sized holes. I trimmed off the excess material, using my memory to guesstimate. At that time, Jai managed to find the original part. Luck was on our side. For grins, we compared my fabrication to the original. It was almost spot on. I do think it would have worked.

 

I took a stab at the spring tension and got the holding screw securely in place (after scraping off the silicone around the mount). I adjusted it counter clockwise a couple of more times to lean it out enough. I would give it some gas, and there was some lean backfire. However, it kept running. It even did well on a short drive down to the paved road and back.

 

Out of curiosity I did experiment with clamping down the return line. The pressure went up to around 60 PSI, and the engine was humming. It responded to the throttle nicely, too.

 

One thing I did not touch was the sensor at the thermostat. It is brittle where the wires come out, and the ground wire look pretty much like toast. I am pretty sure that it's not sending the signal to the ECU that the car is up to temp, causing it to run rich. (I also unplugged the connector for the cold start valve.) Tim said he may have one. I am thinking it needs the parts linked here: http://www.rockauto.com/catalog/moreinfo.php?pk=951105&cc=1209226&jnid=428&jpid=11 and http://www.rockauto.com/catalog/moreinfo.php?pk=4673250&cc=1209226&jnid=450&jpid=1

 

Anyway, I sealed up the AFM with a little bit of clear RTV. The pressure seemed to be dropping VERY slowly. Jai let me know that she checked the pressure about 3 hours after I left, and it was at zero.

 

I'm going to look back at the thread created about a week or so ago where someone was asked about pressure leak down to see what else I can check for. I did not replace the FPR at this time. The next couple of pictures were taken a few minutes apart.

 

I am hoping to go back in a couple of weeks to replace the sensor and implement any other prudent suggestions.

 

 

 

[Redwing]

Home again, towed home again, riggedy jig jig.

Heading out for Church. Started fine, by the time I reached the highway (1mile) starting to run real rough. Drove on, getting worse, not gaining speed with gas pedal pushed hard. Would not go over 30 mph. Then stayed alive but losing speed with no gas pedal help. Just kept losing speed, until when almost no movement, then engine died (1 1/2 miles). Would not restart. Called tow truck. Sigh...

Jai

[siteunseen]

My experience with clamping off the return line, it ran better with more fuel pressure.  I put a potentiometer inline and it runs like a champ now.  Can't speak about the leak down problem though.

 

Steve you're are a true Southern Gentleman.  You inspire me to do better things in my life. 

 

Cliff

[Patcon]

Jai

Did you check the fuel pressure gauge right after it died?

C

[SteveJ]

Unfortunately she did not. She was more concerned with getting the car off the road. I can't say as I blame her.

[gwri8]

Jai, has the car restarted since you got it home?  

 

Steve, I got my boy in school and can make it on the the adventure.  I have both the sensor and the plug that you mentioned.  My Z is getting ready for body work and I do not have an immediate need for them just yet.  Did all the fuel lines check out?  I might have extra hose also.

[SteveJ]

There are some older fuel lines that will eventually need to be replaced. I could use some help on my next trip, as seeing I have limited experience working on the Bosch style fuel injection. Including this car, I have worked on only 1. The fuel pressure gauge helped a lot, as did Tim's advice. However, as described by Jai, there is something happening down the line that is adversely affecting the car. With the fuel pressure leaking down, I am thinking a good FPR may be needed. The fuel pressure does seem a little low. Having an experienced opinion would probably go far in getting a more accurate diagnosis and fix. At least the car is marginally better than when I left the first time. I wish I could have seen into the tank better with the borescope when I visited the first time.

[gwri8]

Well, that makes one more FI car experience than me!   I also have an extra FPR, untested though, came out of a junkyard.  I'll gather a bunch of whatevers that I think might apply (that includes a cooler with ice).  I think Tim might have relatives up near here.  Maybe you could put some family pressure on him to come and we could both learn something from a pro! 

 

Edit to say: There is a 77' in a junkyard in Jasper.  I believe there is a FPR on there, but no AFM.  If not to far, you might want to check it out for other stuff you think Jai may need.

Edited August 16, 2015 by gwri8

[Redwing]

Hi all,

As soon as I got home I had to take a pain pill and lay down. My leg was in some serious pain. I did not do anything before that, only helped the tow truck driver to get her in the carport. That was all I could do at the time.

Just now, I went out and checked the gauge, it was on about 34.

Progressed to starting her. No grinding, she instantly started.

After that, checked the gauge again, and it was around 32.

Both of these events surprised me. I had expected negative results. But I am hopeful that since they were positive that this is a good thing, for the next step of her repairs.

Cliff, yes indeed Steve is a Southern Gentleman 100%. I am so fortunate for him volunteering to help me with my RedBird.

Jai

[Zed Head]

 

The car started up and idled fine. The pressure was around 30 PSI. Around the time the thermostat should open, the pressure went up to around 34 to 36 PSI, and it ran rough. I checked the block temperature with an infrared thermometer, and it was around 180 to 190.

 

After a few minutes, the engine smoothed out again, and the pressure was back to 30. It went through this cycle a couple of more times. During the last time, we tried to give the car some gas, and the engine stalled. 

 

I talked to a friend and all-around Mensch, Tim McGovern, who advised me on how to adjust the AFM. I first thought the spring needed more tension. I adjusted it, and didn't like the results. I adjusted the spring to have less tension,

 

I adjusted it counter clockwise a couple of more times to lean it out enough. I would give it some gas, and there was some lean backfire. However, it kept running. It even did well on a short drive down to the paved road and back.

 

Out of curiosity I did experiment with clamping down the return line. The pressure went up to around 60 PSI, and the engine was humming. It responded to the throttle nicely, too.

 

One thing I did not touch was the sensor at the thermostat. It is brittle where the wires come out, and the ground wire look pretty much like toast. I am pretty sure that it's not sending the signal to the ECU that the car is up to temp, causing it to run rich. (I also unplugged the connector for the cold start valve.) 

 

 

The way to check FPR and pump operation is to remove the vacuum hose from the FPR, if the engine is running.  Or just use the Start circuit if it's not (remove the solenoid wire).

 

The fluctuating pressure is odd.  If the vacuum hose was connected, it was going too high.  If it wasn't it was too low, then got close to correct.  I had an FPR that went rich when it got hot.  Took me forever to figure it out.  One day it finally went way bad and ran really rich and I realized it had to be the FPR.

 

More tension on the AFM spring makes things lean (less vane movement for the same amount of air squeezing by).  If you want more fuel, the potentiometer on the cooling circuit is a better way to go.  Speaking of which, the sensor with the ground wire is actually a switch for the timing advance circuit.  It doesn't really do much, just advances timing by ~6 degrees when cold, through another circuit in the ignition module and pickup in the distributor.  The coolant sensor is the smaller of the two sensors with EV1 (injector-style) connectors.  The thermotime switch has a very large body and wrench flats, compared to the coolant sensor.

 

The fact that 60 psi got things running right suggests that injectors might be clogged or there are vacuum leaks.  That should be adding quite a bit of extra fuel.  Like having 242 cc/min injectors instead of 188 (stock).

[SteveJ]

Thanks, Greg. The next targeted date is August 29th. Is that good for you, Jai?

[Redwing]

Steve,

The 29th is fine with me.

Jai

Edited August 16, 2015 by Redwing