QuestionQUESTION: Dick, I bought a 68 firebird that is pretty much all original but has been restored. It has the original 400 motor (rebuilt) with an edelbrock 4-barrel carb. I dont know much about these older cars other than the obvious (how to change the oil, where to put the gas) but I am learning!! I have had it about a month and it has run flawlessly up to last weekend. I tried to start it and the starter cranked just fine but the engine wouldnt fire. My first guess is the carb was not getting gas. So I replaced the fuel filter (which was packed with rust from the original tank and sending unit) and still no go. Now this car has no fuel pump so the engine has to draw the gas up from the tank everytime you start it. So my question is how does the engine draw the fuel up and where might the no-fuel-to-carb problem lie? Alternatively, do you think there might be some other problem?
Thanks in advance!
-Dan
ANSWER: Well, we'll have to take this step by step.
First, to prove your problem is lack of fuel at the carburetor, take the air cleaner off the top of the carburetor and have someone crank the engine while you spray short bursts of WD-40 down the front barrels of the carburetor. If the car starts immediately, even if only for a second, you have just proven that your problem is lack of fuel, and you can continue troubleshooting the fuel system.
Your car did not come with an Edlebrock Carburetor, so someone has been fiddling in there. Also, the car came with a mechanical fuel pump on the side of the block. There must be a fuel pump somewhere - if not there then there must be an electric pump somewhere else. Follow the fuel line back from the carburetor inlet - you should find it somewhere. If all else fails, try this: turn on the ignition key (without starting the engine), listen carefully, for any noise at all - what you hear will be the fuel pump. Track that critter down and see what is happening with it. Turn off the key, and disconnect the outlet line from the pump, then have someone momentarily turn it back on to see if it is pumping fuel. If it is, look elsewhere for your problem.
Back to the WD-40 test result: If it did NOT start on WD-40, your problem is elsewhere, probably ignition.
Since someone has changed the carburetor, and the Edlebrock has an electric assist choke, we know that modification involved also fiddling with the electrical hook up. Inspect the wiring associated with the ballast resistor and the coil - see if a wire has fallen off or is bare and touching metal somewhere. If you can spot the problem that way, you may be able to fix it yourself. If you cannot, I think you are going to have to take it back to whoever made the modifications and get them to straighten it out for you. This is exactly why I try to dissuade folks from changing from the factory design - every problem requires a pioneering effort to unwind what some previous creative person has done to the poor thing.
If you cannot get in touch with the person who did the work on it, I think you will need to get it to a mechanic who is willing to troubleshoot it for you. By this point, you should at least know whether it is lack of fuel or lack of spark, and if you want to post a follow up question to me telling me what you've learned after the above, please do so and I'll try to suggest the next step for you.
Good Luck - I think you are going to need it!
Dick
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QUESTION: Ok, so I tried your WD40 test (great idea by the way!). The engine fired immediately and ran for about 2 seconds. Based on that I rented an air compressor and blew out the fuel and breather lines between the gas tank (disconnecting at the top of the sending unit) and the fuel pump (disconnecting at the pump). I got lots of crud, some gas, and a clear set of lines. I then repeated the procedure for the fuel line between the fuel pump and the fuel filter (again lots of crud and a clear line). It does have the old mechanical fuel pump mounted low on the front drivers side of the block. After all that I still cant get fuel to the carb. I repeated the WD40 test with the same results. I also disconnected the line to the fuel filter from the pump and cranked the engine to see if any gas came out of the pump. I got no gas out of the fuel pump. My guess is that the fuel pump got eaten up by all the rust and junk in the fuel line. Do you concur? If it is the pump can I take the pump apart and clean it or fix it? Or is the pump strictly replacement only? Lastly, what is going to happen when I take the 2 bolts holding the pump onto the block out? Are a bunch of springs going to go shooting across the room?
Thanks very much for you help!
-Dan
ANSWER: OK, yes, I have one good idea per month. I guess that's it for June, now.
Yes, I concur, your fuel pump has bit the dust (or dirt, to be more accurate). Fuel pumps are not usually something the home mechanic wants to tackle -for one thing, the old rubber diaphragms are probably totally fried by the modern oxygenated gasoline - you need to replace it with a rebuilt or new pump of recent manufacture - they are using much better rubber products in them now.
When you pull the two bolts that hold it on, notice that there is a part pushing on the long arm that sticks out of the pump into the engine - pay attention to how that arm contacts the dingus that pushes on it, because when you put the replacement pump in there, it has to go in the same way. You may have a bit of a hassle getting the arm to fit right, but keep at it - you may have to sneak in there with a long thin screwdriver or the like to hold the actuating thingy out of the way so you can slide the pump in. The pump will try to spring out of the block at an angle because of the strong spring inside the pump pushing on the actuation arm, but you can brute force it into position while you start the bolts. Then the bolts will pull it up tight against the block and all will be OK.
Since this has happened, there is a chance that fuel has contaminated your oil - one of the usual failure modes for fuel pumps is to leak fuel into the inside of the engine past the actuating arm. If you smell any gasoline odor at all on your dipstick, change the oil and filter before you run the engine again. This is important for two reasons: One, the engine could possibly explode if the oil pan is full of gas fumes, and two, gasoline is a terrible lubricant, and your bearings will fail quickly if the engine is run with gas in the oil.
I hope the crud is all gone from the tank now - in case not, carry a spare fuel filter with you so you can change it on the road if you have to.
Good luck!
Dick
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QUESTION: Ok, so I got the fuel pump in no problem. Well, ok there was one problem. I stripped the rear bolt out while I was pulling the pump up snug against the block. The bolt was already half stripped since it fit kinda loose and there was a small oil leak on that side of the pump flange. It appears that this has happened before on my block because the rear bolt is larger than the front bolt already. From this point I am guessing that oil is going to puke out of the rear side of the pump flange at a prodigious rate. But I need to get it to a shop so someone that knows more than me can tap the hole out for a larger bolt. My question to you is this: is tapping the hole out for a bigger bolt my best and maybe only fix? What are the chances I got a few little bits of thread inside the block? I have to change the oil anyway. Do you think I can make a 40 mile drive with one eye on the oil pressure or should I just bite it and pay $400 bucks to get it hauled? I guess I am out for the carshow this weekend.. Bummer! Well there are plenty more this summer.
Thanks again for all your help!
Dan
AnswerYou aren't in quite as much trouble as you think. Yes, there will probably be some oil leak out, but it won't be an enormous amount, because there is no pressure behind it, in fact if your PCV system is working right, there is actually a slight vacuum inside the crankcase, so the only oil that will leak out is whatever splashes up against it - very hard to predict, but I doubt you will be in any danger of running it out of oil.
As for the possiblity of metal pieces getting in there, the action of the bolt threads would be such as to pull metal out, so there won't be much that got in there, and it will settle to the bottom of the pan. The oil pump inlet screen will not allow anything larger than a flea spec to get into the oil system anyway, and then the oil filter will catch it for sure - you have a full flow type oil filter on that engine, so 100% of the oil has to pass through a filter before it gets to the engine internal parts.
If you want to take it to a car show, do it! Just stop after the first mile or so to make sure there isn't an oil gusher there - but if I'm right, you will see only a little drool of oil coming down and back from there.
I take it the new fuel pump fixed the main problem, right?
The mechanic will probably suggest inserting a "heli-coil" into the hole - that is a good fix- it will last the life of the car.
Good luck at the car show,
Dick
