Project240z, 1973 Datsun 240Z

Megasquirt woes, too much fuel?

Chris Hammond

Saturday, October 24, 2009 7:15:52 PM

So I will start this post off staying this: I know nothing, I am a noob when it comes to the megasquirt, and tuning a fuel injection car (or a carb’d car for that matter).

That being said, I think my megasquirt is giving the car too much fuel when it’s trying to start. I don’t know how to prove this, other than to learn how to mess with the fuel map for the megasquirt and see if I can’t back off the fuel a big when trying to start the car. The car doesn’t like to start, it’s very hesitant to do so, and to me it just sounds like it’s flooded and can’t ignite because of this. I’ll have to do some reading here over the next week or so to see if I can’t figure it out and get the car to reliably start.

I did start to adjust the fuel map a bit this afternoon but ended up not getting enough juice from the battery to power the starter and the fuel pump at the same time, so I’ve got the battery on the charge. The charger has been getting a workout today as it was plugged into an 89 RX-7 for a few hours while I charged the battery on that ride up so it can be loaded on the transport truck later today (if the guy ever shows up).

Earlier this week I did manage to get the datsun started, and even backed it out of the garage, but I couldn’t keep it running enough to drive it back in so I had to push it. I moved it over into the third bay so that I could make room for the F250 to park inside for the winter. That truck is huge, barely fits into our 24ft garage (we also have 18” shelves in front of it), but it does fit, so that made the wife exceptionally happy!

I’ll try to get some new photos of the Datsun later this week. I may start doing some body work prep on it, I have a coupon for a maaco paint job for $275, so I think I’ll get some bondo out to smooth out some rough spots and get it ready for paint. Bondo? Maaco? I don’t see any value in putting a lot of money into the exterior of this Datsun at this point. I just need it to run, and not be 5 different colors, so I’ll take it to Maaco for a flat black paint job and be done with it!

Updates from the weekend

Chris Hammond

Monday, May 04, 2009 12:15:41 AM

So I spoke with my Megasquirt Guru last week a few times, and again this weekend, and even had him show up in my driveway to help wrench on the car today!

So yesterday I got up and checked to see if the 36-1 wheel for the Megasquirt (using Ford EDIS) was correctly mounted, meaning, should the mounting have changed due to moving from the 1983 motor, to the 1978 motor. I removed the radiator in order to get to the front of the motor, draining it out was probably a good idea. We had put water in last weekend when getting things ready to start, well the water was pretty darn rusty and dirty when I took it out yesterday, probably need to do that a few more times just to make sure everything gets flushed from the radiator (sitting for 2 years) and the block, which has been sitting for 6 or more years (2+ since it last ran, longer since it actually was used much).

After getting the radiator out of the way I was able to confirm that TDC on the 78 motor is the same as the 83 motor, which makes things easier, I don’t have to have the pulley and 36-1 wheel modified, but it didn’t get me any closer to figuring out why I can’t get the car started.

I ended up bring in the Megasquirt inside so I could hook it up to my Stim and the laptop to figure out if I could see why I was getting a weird RPM signal from it when the computer was hooked up. I wasn’t able to do much there either, but Andy Whittle told me to bring the squirt and the Laptop over to his house on Sunday and he would help me out. Natalie and I went to the gun range, and afterward I had a voicemail from Andy, he was on the way up to my house, talk about service! Andy and I spent a few hours in the garage working on things.

We ended up figuring out that the squirt/stim worked fine on his laptop, which meant that it was a software or hardware issue on my laptop, not the megasquirt. From there he adjusted the fuel map quite a bit, we seemed to be flooding the motor so we dropped a lot of fuel, took all the plugs out and cranked it, trying to get fuel out if it was truly flooded, not much came out.

All in all we weren’t too successful, but we did get it to almost fire up a few times. A few times we got some nice big backfires, once enough that pressure came up through one of the cutouts in the driver’s side floorboard, enough to make my foot jump off the floor. I ended up removing the VR sensor from the 36-1 wheel at Andy’s suggestion and installed a new one, though the plug is backwards on it, so later this week I’ll try it out again, as well as try rewiring the sensor. These sensors are very picky, so we’re not sure if that’s the problem, or something else, but hopefully rewiring it will correct it and the car will start up! Hopefully right? :D

Huge thanks to Whittle for the help today.