[Gestalt1087]

I bought my 1976 Cobra a few months ago, and it's come time to do some wrenching as the fuel pump has gone out. I was wondering if anyone has a PDF of a service manual, or a parts diagram for this car? I know I can chase fuel lines and all that jazz, but I prefer to look at maps before getting into things, and I'm not a professional mechanic, so it also helps me feel more confident.

 

[Guest]

Lots of Haynes manuals available on eBay for $5-$10 shipped. I got mine there as well and it's pretty good (thicker and more detailed than Haynes does for newer cars).

There's not much to replacing the 2.8L fuel pump -- two bolts hold it to the block, you'll need to replace the gasket (will usually come with the pump), and two fuel-lines are connected to it. You may or may not have a cover which needs to be unbolted from the motor mount to do the replacement. It's up at the front driver's side of the engine underneath the power steering pump, towards the motor mount.

 

[Gestalt1087]

It turns out, the fuel pump isn't the issue the wiring associated with the pump isn't getting any juice, so therefore no pump. I replaced the wiring and nothing has changed, but the fuse seems to be intact. I haven't replaced it yet, but I checked it out and it looks fine.

Currently at a loss.

Also, thank you so much for your reply.

 

[Guest]

This is an aftermarket electric fuel pump? The fuel pump on the stock 2.8L is mechanical and bolted to the block (no wiring).

 

[Gestalt1087]

I went underneath the car and looked at the tank, and it looked as if it had an in-tank electric fuel pump. I obviously could be totally wrong on this one. I'm going back up there Sunday to make sure I'm not completely being an idiot on this one.

Luckily, I just ordered a Hayne's manual for it that should arrive on Monday.

I get the feeling I don't know what's up from down with this car. The fuse box is super awkward, I definitely couldn't find a mechanical fuel pump to replace under the hood, and it really does look like the tank has an electric fuel pump in it.

 

[Guest]

What you're probably seeing is the fuel sender. It's on the front of the tank (towards the axle), there is likely one hose, which is the fuel line, and the pressure sending unit (a two-wire connector that goes to the gas gauge). The fuel pump sucks the gas from the tank. This makes the car prone to vapor lock, fuel-line-freeze, and long cranking if it's sat a while (which is why electric is an improvement). The fuel pump is on the block, I promise, I have the same engine.

If you're used to fuel injection, a carbureted old car is definitely going to take some getting used to. If the unit you think is the pump has only two screw terminals, it's just the sender. I hesitate to speak in absolute terms because a 37 year old car has had many chances to be modified.

 

[Gestalt1087]

You were absolutely right on all accounts. This car hasn't been modified at all aside from replacing parts that have worn themselves out over time.

I've gone through all the lines, I've tested the pump separately and it seems to be working, so I'm not entirely sure what I'm encountering here anymore. This whole thing definitely has me scratching my head.

 

[Gestalt1087]

Also, thank you for your responses. I just got the manual in on Friday, but I have a feeling I'll still be looking for outside information.

 

[Guest]

You're welcomed, just let me know however I can help! Quick way to test a fuel pump is to just disconnect the fuel line as it enters the carb, put the rubber hose into a container, and crank the engine.

Basically you're looking at two major conditions to cause a no-start, no fuel and no spark. Remove one of your plug wires, put an old plug into the wire boot, put it up against the metal of the car somewhere and crank to see if you have spark.

As for fuel, it's possible that the fuel pump is working but that the car still isn't squirting fuel into the engine. If you verify the fuel pump is working (step above), then remove the air-cleaner assembly and get a flashlight to check inside the carb's front plate (you may need to use a screwdriver to open the choke plate if you have an electric choke which is holding it closed). Open the throttle using the lever and see if you can detect two distinct streams of fuel being squirted out onto the lower throttle butterflies.

That was the cause for my no-start problem on my '78 with the 2.8 (the accelerator pump diaphragm had dried out and become brittle so it wasnt' squirting fuel into the carb even though the pump was working). Those things were supposed to be changed every couple of years and it's a good safety measure too since a leaking accelerator pump can leak onto the engine.

If that's your case as well, dripping a little fuel down the carb (or using starting fluid) will help get it to start.

 

[Gestalt1087]

So, I replaced the mechanical fuel pump with a new one and it is running pretty well, but still occasionally shuts off. I wonder if this is just something that I'll have to acclimate to if I use a mechanical fuel pump?

 

[Guest]

It should keep running steady, mechanical pump or not. Shutdown is possibly related to a vacuum leak (more of those old, dry seals). Try removing and plugging accessory vacuum lines one at a time (clamp off brake booster vacuum hose (while stopped don't drive like this), PCV valve, EGR valve, distributor advance, purge canister, heater controls) and see if the situation improves.

Your carb may also need to be adjusted (idle screws under the base of the carb on the front side). You should adjust mixture for max vacuum at idle. Adjust your idle speed as well.