MaxxPayne

I'm Having acceleration issues (in gear only) I can rev car up no cuts, but when driving over 30mph or up a hill it will stall out on me. Suspecting it's a failing fuel pump, but to be sure I want to do a fuel pressure test. its a 1979 so there is no schrader valve. could someone please tell me how would I would do a fuel pressure test with out this while in park. I want to test the fuel pressure to make sure it is correct so I can rule out fuel a issue before I look in to replacing the ICM, and double checking that my timing is correct, and making sure my idle mixture screws (a/f ratio) are tuned properly with a vacuum gauge.

Aussie79

Just replace the pump, it is cheap and easy to do, getting to the bolts requires the car jacked and passenger wheel off, get to them with a long- long extension on a socket but other than this its a 1 hour fix and less than $60. Forget pressure testing, from your description of the fault it is almost certainly a pump. If you really want to test it just undo the hose at the carb, remove the small filter and replace hose, if it runs better its fuel pressure, the filter has a non return valve which takes a couple of pounds to overcome it, removing the filter gives you those extra pounds of pressure. But if it were me I'd just do the pump and drive it.

Cheers, Dennis.

MaxxPayne

Hey thanks man that is what everyone keeps telling me. I got small 2 ton hydraulic jack and a jack stand to use, but idk if u can tell by my picture I put hooker header side pipes on it so do u think it would be a good idea to jack it up in fount or behind the passenger side tire on the frame somewhere. I think theirs a little clearance behind but its really close with the exhaust and the car sits so low would it be ok to jack in fount of the tire?

Also I got a 3 piece AutoCraft Fuel Line clamp Set AC3380 just in case I need to clamp the fuel line that is going from the tank connecting to the pump so when i do change it i don't get fuel everywhere Is this needed, if so do I need to clamp both fuel/return lines

Now I just got to order the new stock pump, and a fuel line from pump to carb. would i need the 90˚elbow for the pump as it says on the site i might using zip-corvette.com

Thanks again!

DUB

Too many variables can cause this problem.

BAD fuel, plugged or almost plugged fuel filter. Supply hose is getting sucked shut or is kinked and will then collapse due to not having the correct formed 'S' supply hose.

Float may be set low in the carb and starving for fuel...and not knowing what type of carb you have or a picture of your engine compartment...I have to stop there on this.

A plugged or nearly plugged catalytic converter....if you still have it or them installed.

Timing issues or ignition tune up parts needed. Not knowing how well it idles and if you have a vacuum leak or not.

I would do a fuel volume test on the pump....and there is a way to test the fuel pressure without a schrader valve...but I am a bit scared to tell you how to do this. Not knowing your skill level and tools available. I do NOT want to be remotely associated with you having a "Joan of Arc" situation.

And it is possible...that the heat from your headers can be adding to a problem....not knowing if this problem was there BEFORE you installed the headers. HEAT + FUEL = POTENTIAL PROBLEMS.

DUB

scottyp99

Siphon as much fuel out of the tank as you can before you start, and jack up the front of the car. When you remove the fuel line, just let the fuel run out into a clean bucket until it stops, then do your work. If you are replacing the fuel pump, it's probably a good idea to replace the two rubber fuel lines connected to the fuel pump. Don't just use rubber fuel line off the roll down at the parts store, order the correctly shaped lines from one of the suppliers.

Don't jack the vehicle up from anywhere in front of the front tires! The frame rail right behind the front tire is safe. Remove the sidepipe if you have to.

EDIT: I just your other thread where BKbroiler tells you to jack it up by the front crossmember. I guess that would be OK, but for Pete's sake, be extra, extra careful!

As far as the 90 degree elbow, your stock pump-to-carb line should attach directly to the pump if it's a stock replacement (which it should be) Good luck, and let us know how it goes, and if you get into trouble, let us know, we'll do what we can to help out.

Scott

MaxxPayne

Well I put in high grade gas and a fuel clean additive to make sure it wasn't something like that and I also changed the fuel filter. so no I can only believe it would be the pump. I plan on buying a new stock pump with a new Fuel Pump to Carburetor Line and also plan on replacing the Fuel Pump Gasket and Fuel Pump Return to Fuel Line Hose as well as the "S" Frame Line to Fuel Pump Hose.

no idea how float works I hope the mechanics I took it to didn't mess with the carb. I know it ran fine and great no issues until I had a new radiator put in. Its a holly remanufactured rod qjet 750cfm I believe.

with the side pipes and slip in mufflers I've had for the past 5 years had no issues so there is no catalytic converter

It was timed properly when I put in a new diet many years ago just again asking cause who knows if the mechanics ****ed with it they seemed pretty dodgy

I'm skipping the whole fuel test thing and just gonna put in a new pump with fuel lines and flex hoses now.

MaxxPayne

I have a full tank of gas so not sure if I feel comfortable doing a siphon i have fuel clamps I could use or someone mentioned to plug it with a bolt I planed on replacing the flex hose's as well found on this page http://www.zip-corvette.com/68-82-c3...7226&year=1979

the Fuel Pump Return to Fuel Line Hose and the "S" hose. Im actually nervous to jack it from the front so I'm gonna try to do it from behind the tire on the side of the frame but with side pipes theres not much room to do so and they are welded on so i can't remove.

I didn't think i would need the elbow but just wanted to make sure Thanks everyone so glad to be apart of the forums for help much appreciated will keep updated! cheers

scottyp99

Just siphon the gas out into a gas can, and dump it into other vehicles. (You don't want that much gas sitting around in open buckets, man!) I'm telling you, it'll make your life a whole lot easier.

Scott

MaxxPayne

As much as a good idea of that sounds I only have one 5 gal gas can. in my car its a full tank so ruffly sitting around 20 gals. Also I would really have no where to put the remaining gas If i wanted too. I don't have no large buckets sitting around that I could temporarily use. Shouldn't the pressure be cut off with the car jacked up making it not gush out? also is there any tricks to not let it come gushing out like disconnecting the battery or gas cap from the tank to relieve pressure? only think I'm really able to do is try and plug the hose before the pump with a fuel clamp or plug it with a screw.

DUB

FACT!
If you buy a stock fuel pump...you WILL need a special 90 degree elbow with a 3/8" flare fitting in it if you plan on using a factory 'pump to carb' steel line. The fitting on the bottom of a stock pump is pipe thread...and the fuel line is not. Not only that...the fitting on the bottom of the fuel pump IS NOT positioned so you can attach the steel fuel line directly to it. I WISH it were that easy....but it is NOT.

You do not need to siphon out fuel to do a fuel pump replacement,. I NEVER DO.

I put a plug in the supply hose after it has been removed and move on. Sometimes I will even remove the fuel cap...and with compressed air...under very light pressure...blow air into the fuel supply hose and blow the fuel back into the tank...and when doing this...the fuel will not drain out. The fuel tank can not drain out of the return line. Only the fuel that is in it at that time will come out.

DUB

MD Auto

How to check fuel pressure on a carbureted Corvette . Step one open hood .... Just kidding . At the fuel inlet at the carburetor remove the fuel line ...ONLY USE A TUBING WRENCH !!!!!!THIS IS A MUST !!!!! Also you will need a back up wrench on the fuel filter housing THIS IS A MUST !!!!! If you do not use these you will A. round off the flare nut ..or B. twist the fuel line at the flare nut or . C ...BOTH!!!! Once the fuel line is off get some 3/8 rubber fuel line about 3 to 4 feet long and a hose clamp . Push the flare nut back some install the 3/8 fuel line over the end of the flare and install hose clamp . disable the ignition system . this does not mean just pull the coil wire ...It means disconnecting the positive wire from the ignition coil and wrapping it with tape so as not to short to ground. Then with a PROPER testing gauge I.E. vacuum / fuel pressure gauge bought from a tool truck or parts store connect it to the other end of the fuel line you installed on the steel inlet line use a hose clamp . Crank engine while observing the gauge. It should pulse 3 to 6 PSI while cranking. Then disconnect gauge and do a fuel volume test . With a strong battery and the ignition system still disabled . Secure the end of the 3/8 fuel line in to a gallon container , preferably with measuring marks on it . Crank the engine for 30 to 45 seconds straight , you should have a steady strong pulsing stream of fuel somewhere around a quart or so . Voila !!!!! Thats how to safely test a fuel pump . While your there replace the fuel filter !!!!!!!!!