After a year of frustration trying to get the EFI to work, I decided to go back to basics. I removed some of the EFI components, such as the throttle body, and pushed aside and secured the wiring. Then I rebuilt the Demon carburetor and installed that.
The engine still refused to start after resetting TDC. What I got was a backfire through the carburetor. My guess was that the air/fuel mixture was collecting in the intake manifold and getting lit by a spark plug through an open valve. But that shouldn’t happen if the valve train is operating correctly. I removed the valve covers and checked to make sure that the valve train is operating normally — seemed alright.
I posted the problem on the Squarebirds.com Forum*. One of the experienced members agreed with my analysis and suggested this solution:
“You are correct, backfire is usually produced with spark happening when a valve is open. That can happen if adjacent spark plug wires leak, your distributor cap could have a carbon trace, your timing set is off a tooth, etc. Let’s start at the beginning with the key OFF…
- Remove your valve cover to expose #6 rocker arms and remove your distributor cap.
- By hand, rotate your crankshaft via the damper bolt. When #6 exhaust valve is nearly closed AND when #6 intake is just beginning to open, right there when both rocker arms are dead level, STOP. (Use a straight-edge on your rocker arms.)
- Look at your timing marks. They should be at TDC and your distributor rotor should be pointed at #1 spark plug tower (“1” is normally molded into the cap).
Notice that #1 and #6 pistons go up and down together. When #1 is firing, #6 is on its exhaust stroke (look at your firing order). If the cam timing is off, your damper’s timing marks will show which way and how far it’s off.
If your distributor is off, the rotor will not be pointing at #1 spark plug tower. Remove the distributor and reseat it properly. At about 6-degrees BTDC on your timing marks, your points should open. Rotate the distributor until the points just start opening. Here, you can use a continuity light. This will get your engine running. You may fine tune with a timing light or vacuum gauge afterward.”
He was correct in that the distributor alignment was indeed off a tooth. After performing the above procedure, the engine started right up. Hallelujah.
The plan is to get some enjoyment from actually driving the car. After a few months, when I’m sure that it’s running reliably, I’ll take another shot at the EFI installation.
*I highly recommend the Squarebirds.com Forum for any classic Ford owners!
The EFI system components are installed and wired in.
All that remains is to put gas in the tank and fire it up. But before putting gas in the tank there has to be a way of determining how much gas there is in the tank. Fuel in the tank is measured by a sending unit comprising a float attached to a variable resistor that is sealed in the tank. The amount of fuel floats the float, which changes the resistance. The resistance is wired to the fuel gauge on the dashboard, which measures the resistance to indicate the amount of fuel.
The sending unit in the my tank wasn’t varying the resistance (i.e., it was broken), so the sending unit had to be replaced. As with any old car, parts are sometimes difficult to obtain. Although there was a replacement part listed in several catalogs, the part was nearly always out-of-stock/unavailable.
Another consideration is that the resistance range of the sender has to match the range of the gauge. Although I eventually found an in-stock sender I was not able to determine what the resistance range was prior to purchase, so I’ll have to wait until the part arrives and measure the range. If the range doesn’t match my gauge I’ll have to find and purchase a gauge that matches the sender. This is why working on old cars can be a pain in the ass, costing time and money.
Kudos to Pat Wilson’s T-bird Parts for their fabulous customer service! Thanks, guys!
The Electronic Fuel Injection (EFI) system requires an oxygen (O2) sensor in the engine exhaust to regulate how much gas to inject into the cylinders.
“The oxygen sensor is a critical component of the electronic engine management system, and relays real-time air fuel mixture data to the computer for minute adjustments to fuel mixture. When air and fuel enter into an engine’s cylinder and are ignited by the spark plug, the resulting exhaust gasses contain trace amounts of several elements such as nitrogen, oxygen, etc. The more complete the burn, the less oxygen is present in the exhaust gas. So, through interacting with the unburned oxygen in the exhaust, the sensor produces an electrical signal which the computer interprets as a rich, lean, or stoichiometric condition (the ideal 14.7:1 air-fuel ratio at which gasoline and air burn optimally). The EFI computer (ECU) can then take that information and use it to influence the amount of fuel it injects. This is called closed loop operation, where the O2 sensor actively influences the ECU’s fueling strategy.” (https://www.holley.com/blog/post/explained_holley_efi_sensors_and_what_they_do/)
The O2 Sensor must be inserted into the engine’s exhaust stream, which means drilling a hole in the exhaust pipe to insert the sensor, which is threaded into the hole. Unfortunately I misjudged the amount of clearance to the under-body when I drilled the first hole (red dot). I had to seal that hole and be more careful selecting a location for the sensor. The green dot is where it fits with room to spare under the car.
Once the sensor is installed and the pipes reconnected to the engine I can wire up the system, which I predict will be a much easier task.
Since I last posted, we sold our house in Atlanta. Meanwhile we lived temporarily in our second home while our new house was being built. Much of what we owned, including the T-bird, was put in rented storage. The Bird stayed in storage for about 9 months. Our new house has a 3-car garage with work shop space, a significant step up from working on cars outdoors.
I replaced a leaky coolant pump with a high flow pump from Summit. Removing the old pump entailed removing the electric fan and the bracketing that supports the aftermarket A/C system, much of which is bolted to the coolant pump. Luckily I was able to do that without actually disconnecting the A/C or removing the radiator. After installing the new coolant pump and reassembling the brackets, the car started right up.
To further ensure that the car won’t overheat (a previously annoying problem), I’ve wrapped the exhaust pipes with titanium mesh heat wrap.
The test drive got only as far as the community stop sign, where it stalled and wouldn’t restart. I had to tow it back the ~400 ft to my garage with my truck. The problem is that the carburetor was not set correctly. So, I got the carb set up so that it ran OK and the test drive was good.
But I wanted it to be fine tuned by a pro. I went to a small speed shop in the neighborhood. He told me the gas had been in the tank too long and had gone bad. The fuel system had to be flushed out, the tank cleaned, and the carb cleaned out (possibly rebuilt). I removed the tank and cleaned it out with acetone, flushed the lines and replaced the fuel filters. I removed the carb but decided to replace it with Electronic Fuel Injection (EFI).
I’ve received the computerized EFI system from Summit and an Edelbrock high-pressure fuel pump. Will post more as I install the system.
I have finally sorted out basic drive-ability issues. Beginning to lengthen the drive distances as I gain confidence in the car’s reliability. There is still a lot of work to be done to restore driver/passenger conveniences and cosmetics. Here is a short video of the current state of the vehicle.
Now that the engine work is bolted down (as opposed to screwed up) and the car painted, the last major tasks are to carefully reassemble the numerous pieces that were disassembled for the renovation, such as interior conveniences and exterior trim (e.g., chrome). As can be seen in the first photo, the grill and bumper have been attached. One of the lower bumper guards was damaged beyond my ability to repair but I found two for sale at reasonable cost on Kijiji, Calgary Alberta (Kijiji is a Canadian “Craig’s List”).
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Weatherstripping and seals had to be installed on the door and interior door panels prior to installing the windows and the doors’ interior parts (door locks, stereo speakers, etc.). Window cranks and door locks were cleaned and lubricated for smooth operation. The doors now close with a solid, satisfying “thunk”. (Beats holding them closed with bungee cords while driving on the highway.)
There was still a problem with the engine quitting after getting hot, so the fuel line was moved again: this time up against the firewall so that it doesn’t cross over the hot engine (see photo). Also had a chance to lean out the carburetor fuel mixture. The engine was running too rich and fouling the spark plugs.
They’ve been taking their sweet time getting it done, but I can’t complain as to their attention to detail. They insisted on redoing some of my body work (included as part of the quoted price) and the re-sanded, primed car was indeed highly professional quality. After urging by me to please move it along, this morning they sent me some pics of their progress.
Click to enlarge
Green arrows indicate dents or rust that was repaired. Self-etching primer applied to exposed metal. Still need to smooth body glaze on minor irregularities and pinholes, then spray on epoxy primer. (Click any photo to enlarge.)
Pics of the interior, before and after. Note recovered dash pad and new upholstery.
(Click to enlarge)
My 390 FE has a hot camshaft and a Street Demon 4-barrel carb. It’s been trouble tuning it to optimum. It’d be running fine and then, for no apparent reason, stall. Restarting afterward often problematic. The car wasn’t being driven enough because I had no confidence that it wouldn’t leave me stranded on the road far from home. Had always thought that this was due to my inexperience in doing a proper tune-up. So I took the car to a shop specializing in performance engines and had them do the tune up.
When I picked the car up it ran better than it ever had before. It drove fine through the surface streets leading to the highway and then ran OK at highway speeds. But after about 10 miles, off the highway in stop-n-go traffic, it stalled again. It would restart but stall when put in gear. After several start-stall iterations, it died completely. Had to tow it home. The next day I got it started (using some canned starting fluid) and was able to drive it a short distance.
Started it again a few days later. After a full warm up, it idled smoothly for about 5 minutes and then faltered and died. It was beginning to dawn on me that the problem was more than what a tune-up could remedy.
Suspecting a possible problem with the stock mechanical fuel pump, I compared the specs for the Demon carb and the stock fuel pump. The input fuel pressure range for the carb was slightly higher than the output range of the pump, although the nominal numbers did fall within both ranges. However, the pump was old (the original). So I decided to install an electric fuel pump.
The carburetor manufacturer suggested the Mr. Gasket Model 12S as meeting their pressure and flow specs. The new fuel pump solved the problem of erratic engine behavior and sudden stalling. Here are some pictures of the installation. (Click each to enlarge.)
Fuel Pump Relay in Trunk. Wiring to battery and fuse box is routed through center console.
Secondary Fuel Filter. Primary fuel filter is mounted to Fuel Pump.
Fuel pump mounted under car forward of fuel tank in rear axle well. Flexible hose is protected from road damage by routing it through a steel spring.
Circuit breaker for fuel pump, connected to battery + at starter relay.