TheSilverBuick's 1967 Thunderbird

[Scott Liggett]

good work.

[mustang13]

Randal, you are a Fuel Injected mad man!

What is your MPG goal with Big Bird!

[TheSilverBuick]

Well the Autoleak regularly got 17mpg on the highway, which isn't too bad. I did a little datalogging with the MS1 and the carb on there, and it was clear the carb was set for it as the AFR's were real solid 13.5:1-14:1, and this is at 6500ft elevation, so it'd likely lean out some at lower elevation. I'm hoping with the coasting fuel cut, etc. to get a couple mpg's more, 20?? I'd be happy with 17mpg still as long as it starts better and has more throttle response.

[TheSilverBuick]

I seem to of ran into a mechanical hiccup. It's looking like one of the injectors isn't working properly One injector is spraying a ton of fuel and the other is barely spraying anything.....

So there are few questions I need to figure out. Was it a setting I had that possibly cooked one injector? Is there contamination in the fuel line that took it out? Or is there a simple loose wire some where in the line? I guess I'll go out there and start looking. New injectors are $100 a pop :o plus a TBI rebuild kit.

Still fires up easier than the old carb.


*A little further update, after turning the car off, one of the injectors is dripping, I don't think that's normal.

[TheSilverBuick]

Ok, I suspect perhaps the TBI may just need a simple rebuild kit, and possibly just the seals around the injectors are leaking.

Reading some quick google search results, my under producing injector is likely fine (I've turned the fuel way down trying to lean it out, apparently compensating for the other injector), and my over producing injector (the one that also drips after the engine is off) likely has a bad seal. I'm guessing from all the shelf time this e-bay TBI's had, it probably needs new seals and gaskets. I'm also supposing that when I had it running off the stock mechanical pump, at what is likely less than half the TBI recommended pressure, there wasn't enough pressure to blow by a bad seal, at least not in any great quantity. I had not looked at the spray pattern until today since putting the fuse back in the electric pump, and the electric pump pressure I think may of done her in. So I'm going to go see what the local parts stores have in stock. Wish me luck

[TheSilverBuick]

Well neither part's store had standard GM TBI rebuild kit in stock, it should be in on Tuesday So I'm going to park the T-bird out of the way and bring the Skylark around At least it runs, pretty well even, just 11.5 pig rich :P


For a little back story on the tuning issue with the leaky injector. Prior to noticing a mechanical issue I could program the system to run ultra lean, basically the megasquirt tells the injectors to add very little fuel (base fuel was set really low) and it'd idle nice and sweet with a 14-15:1 AFR (livin off the leak), but when it came to driving the car, the amount of programmed fuel had to be turned waaaay up because it'd go dead lean and the VE table needed waaay to much change to be normal, and even then the base fuel amount was too low to properly add enough for loaded up driving. So switch it over to where I have it programmed now, it's waaay rich at idle, I have a normal base fuel setting and the VE table programmed to add essentially no fuel (why I thought one injector wasn't working) and it'll idle rich, but it runs hard (and rich) loaded up in gear. So I can move it around but I won't be driving it too far like this.

[TheSilverBuick]

Well I think I cooked an injector The o-rings were good, the whole inside of the TBI looked great. As soon as the electric fuel pump kicked on (for the five/ten second prime) one injector just pours full bore while the other remains pretty much dry

I found a set of injectors on E-bay for $70 a pop, so I bought two figuring if I cooked one with the settings, the other could be on the fence.... Should take me less than five minutes to swap injectors once they show up.

Got to be careful with low impedance injectors Live and learn.

[SuperBuickGuy]

Sunday I'll look for the injectors I pulled off my 93 Chev pickup.... problem is, I have no idea where I put those things (it was 2 moves ago).... if I find them, they're all yours.

[TheSilverBuick]

Sunday I'll look for the injectors I pulled off my 93 Chev pickup.... problem is, I have no idea where I put those things (it was 2 moves ago).... if I find them, they're all yours.

Don't worry too much about it. I learned that OE injectors are of a different design, plus OE injectors have a lower fuel flow rate. Infact I learned the current injectors I have are obsolete, and the kit to convert it to the new injector styles is $100, plus the cost of two new injectors.

[dieselgeek]

are you sure the injector was killed with software settings? I've never seen this happen. I've seen improper use of PWM kill an injector driver in a megasquirt, so make sure it's not your MS that's toasted. (it's a cheap and easy fix if you did kill the injector driver circuit).