Slow Car Fast
December 20, 2010 - It's been a busy few days.
On Friday night, Janel and I took the MG out to run an errand or two - which turned into a big grocery shopping trip as well as other events. Of course, I had just adjusted the rear hatch and it refused to open again. So we had to load all the groceries in through the back seat. A tip for those who are planning to use an MGB GT for a station wagon - anything you put in the back is on clear display! Unless you stash it in the smuggler's hole underneath where the spare tire lives. Anyhow, a bit of lubrication when we got home and the problem was solved.
We also got a little hiccup when the engine died a block from home. It fired right up again, but that was a bit odd. My suspicion was low fuel.
The next morning, I jumped in the car to go to the opening of a new car museum close by the house. While sitting at a stop sign, the engine died again and would not restart. Banging on the bottom of the tank gave a very empty BONG, so my chase car (a Miata with a 480 hp LS3, of course) took off to get some fuel. My theory was that the fuel gauge (the original, on the original sender and wiring) wasn't quite calibrated right - or, as a safety margin, it never went completely to E because then it would appear to be not working!
The fuel arrived. That didn't work. Bill Cardell (the driver of the Miata) and I figured out the fuel pump wasn't running. And then it was - there must be a slightly dodgy connection in the system somewhere. I got to the museum and back without incident, but it really highlighted that I'm not just debugging my own work over the last two years, but also a 38-year-old British car that never really functioned fully when I first got it.
I'd like to point out that it's not a Lucas fuel pump, but a good Pierburg unit. Just before the Lucas jokes start...
The photo? I just like the way the car looks!
entry 510 - tags: debugging
June 23, 2011 - So much for all the basking in glory.
I was driving home last night and the MG started to stumble for a bit, then coasted to a halt. It acted like it was out of fuel. This has happened before. Luckily, I was following my coworker Brandon home and I was only a couple of blocks from his house. So he grabbed a couple of items and we tried to fix it.
First, I checked that there was power to the fuel pump. Yup. We threw in some fuel, just in case. No change. The pump sounded a bit off, though. Strained. We sat there and kicked around a number of ideas such as clogged inlet screens, overheated fuel lines and the like. Finally, we decided to grab his trailer and just drag the car back to my place where I could troubleshoot in a more controlled environment. When we went to start the car to put it on the trailer, there was no fuel pump noise at all. A quick feel under the car and I found a power wire that was no longer attached! It had come off the ring connector. Aha!
I used a bit of electrical tape from underhood to tape the wire to the terminal, just enough to get the car running and on to the trailer. That got me home.
The connector is one that came with the pump. I didn't have any ring terminals in the mini size used, so I'd just reused the connector and spliced the wire into my harness. So this time, I cut off the spliced wire and crimped in one of my own, complete with heat-shrink. That should solve the problem. The car fired up happily so that must have been it. It's expected that a car that's had this much work performed would have some trouble.
entry 598 - tags: fuel, debugging
June 23, 2011 - Ah, nuts.
I spent a couple of hours running around some local roads shooting a bit of video and generally having fun with the car. The exhaust noises started coming back as the car got hot, but otherwise it behaved itself. Even with an ambient temperature around 95F or so, it didn't have any overheating problems. It did act a little cantankerous on a couple of hot starts, but cycling the key solved that. Quick car, let me tell you. The video will be along soon.

But unfortunately, the fuel problem returned. After running happily for all the video, I was heading home when the car started to stumble and then died in front of a gas station. I pushed the car into the lot where it was safe, and started poking around. My electrical connection seemed fine, but again the pump sounded a bit labored when it ran. I could sometimes get the car to fire up, but it would only fire a cylinder sporadically, just enough to keep it turning over but not much else. So I left the car and occupied myself elsewhere for half an hour.
When I got back, it fired up happily. I made it almost all the way home before it stumbled to a halt again. I parked it by the side of the road and again, a half hour later, it fired up.
So whatever is wrong is probably related to heat. I'm thinking it might be the pump itself. The pump I'm using is one that was sitting around my garage, and probably last saw action a decade ago. Foolish, maybe. But it's been working happily so far. The pump is fairly well protected from heat, although there is one of the exhaust pipes about a foot away. It doesn't feel hot to the touch, nor do any of the fuel lines.
It's possible that the input screen on the pump is clogged. Because the filter is also the regulator, the pump is pre-filter. It's quite likely there was a bit of debris in the tank despite my best efforts. I'm not sure that would manifest itself quite like this, but I'll investigate it none the less. I'll probably just swap in a new pump of the same type to be sure.
entry 600 - tags: fuel, debugging
June 26, 2011 - I swapped out the fuel pump yesterday.
There were none of the hoped-for obvious problem signs - no big chunks of gas tank stuff clogging the inlet, no damaged wiring. Nuts. A drive today in hot (95F) weather unearthed no problems with the fuel system, but it drove fine almost every time before. So the jury's still out. I hate it when things are inconclusive like this.
We did find one definite problem, though. The car is very well ventilated, quite livable even in our hot climate. But when Janel drove it in open-toed shoes, she discovered that increased speed pushes some air through the heater core and directly on to her feet. Now, the heater core is still running coolant through it as I wasn't sure when I hooked things up if the LS engine could do without that particular circuit. Apparently it can, and so I am under orders to fix that particular problem quickly before her feet melt. I'll have to see if I can find the old heater valve again.
Other than the hot toes, she did bond with the car. Especially when she was trying to merge and wasn't sure if she had enough room. I told her to punch it, she'd have enough room. Yes indeed she did. She laughed and started looking for opportunities to open the throttle.
entry 603 - tags: debugging, heater, fuel