Ford Muscle Cars Tech Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter · #1 ·
I just installed my 87 rebuilt 460 in my F350 4sp. I went with a Biggs 750 carb that the guys tested and set up before shipping to me, and D.U.I (Davis Unified Ignition) distrubitor and their one wire Ford alternator. The engine starts right up, but runs at high RPM for aprox 5 -8 seconds and sounds great, but then dies. As my F350 has duel fuel tanks, I Have two "T" fittings in my custom 3/8" steel fuel line feeding the carb. One handles the fuel coming in from the front and rear tank, exiting to the second "T" which feeds the carb inlets. I Have good compression, oil pressure, and I assume good vacuum, and it appears enough fuel flow as the accularator pump in the carb does spray fuel when pumped by hand. The truck has a low pressure fuel pump in each tank, with a high pressure pump mounted to the frame, with a tank selector valve. I get the same symptoms from either tank. I did eliminate the Ford "T" where the two tanks converged, which suspect had a check or regulator in it, but did close of one tank line to eliminate back feeding but there was no change. It still seems like a fuel starvation problem to me, but the very high starting RPM leads me to think excessive vacuum? or timing advance ( vacuum line is disconnected and plugged) or perhaps the ignition ss cutting out after a few seconds for some reason. Does anyone have any ideas on how I can further troubleshoot this problem?
Thanks
DAustin
 

·
Premium Member
Joined
·
34,855 Posts
Throttle plates open too far/Vacuum leak (the same results come from either issue).
It could be something getting hot then shutting off the spark. How to trouble shoot it:

Keep the vacuum disconnected. Turn down the throttle screw. Pull ONE plug wire and place a grounded plug on it to watch for spark.

Then start it up again for that 5-8 second burst keeping an eye on the plug to ensure that it is firing still when it dies.

If so see fuel delivery (float level too low or debris in carb?)

If it stops throwing out spark at the moment it dies then you have an issue between the dizzy and the ign.

FE

_________________
Thou Shalt NOT Mock My sissie Falcon!

<font size=-1>[ This Message was edited by: FEandGoingBroke on 7/6/06 10:42pm ]</font>
 

·
Registered
Joined
·
1,250 Posts
Waht fuel pressure do you have at the carb.
Fule injection puimp pressure is way too high for needles and seats.
Did you install a pressure regulator?
 

·
Registered
Joined
·
448 Posts
I have a similar problem with mine and so far have tried everything i can think of, Would be interested what you find if you can get it running, if i get mine going i 'll do the same, i,ve repaced the intake gasket, timing set, tried 2 different carbs and reset the valves, mine starts up and as long as the choke is on or i hold the gas pedal it seems to run good ,as soon as I let the pedal go the idle falls to very low and the car dies, checked spark at the dizzy and it seems OK rebuilt the electric pump and all have not helped ,so if you discover the probelm with yours please post it here, i've been chasing mine for over a week now
 

·
Registered
Joined
·
10 Posts
Discussion Starter · #5 ·
Thanks for all the info. I will be working on it this evening and weekend. 1st check will be the spark test, and fuel pressure check. I think I will lift the Edelbrock intake and reseal also, I used a 1/4" bead of high temp RTV on the ends instead of the seals and Edelbrock gaskets as they recomend - but wonder if a faulty end seal (RTV) leak could be causing a vacuum leak? Good Luck Fomoco8 I am heading in the same direction as you - I'll let ya know when I find something.
 

·
Registered
Joined
·
908 Posts
Pull the sight plugs out of the fuel bowls, and run the electric pumps. See if fuel trickles out of the holes. If not, raise the float levels a little till a little fuel does come out with the pumps on.

Fire up the engine. As it starts to die, pump the accelerator pump by hand, without moving the throttle. If the engine picks right back up, it is running lean.

Disconnect and plug ALL vacuum lines and try again.

If there is no change, try setting the idle mixture screws to 3 turns out and fire up again.

If this doesn't work, you likely have either a MAJOR vacuum leak (unlikely on a 460) or the idle circuit in the carb is plugged up.

Greg
 

·
Registered
Joined
·
448 Posts
Well i tried all the tricks listed here and no luck, however i did find a brand new oil leak that it didnt have before i replaced the intake gasket, i guess i didnt put enough RTV back there and found a large puddle of new Castrol GTX in the well around the oil pressure guage, double checked the sender area it was dry , intake edge at the back wet, Oh well I didnt have anything planned this weekend anyway, Still trying to figure the problem out and in my mind its an intake issue but where I'll have to find, this problem came out of the blue and wont go away no matter what so i'm gonna have to look a lot deeper into it, it always ran good . hell i''m wondering if something cracked or is broken , may have to do some PT testing on it,
 

·
Registered
Joined
·
448 Posts
Hey daustin, I got lucky today and swapped out the Holley i was sure worked fine and put the Proform body and Quickfuel Base on and the thing runs and not bad either,new timing chain helped it too, but that damn Holley would not idle, as soon as I hit the new set up it ran great, gotta tweak some stuff and readjust the solids but it is living. plugs are starting to grey and the only 2 issues it has is it went up to 180 pretty quick even with a new 160 thermostat and the backof the intake is leaking I guess not enough RTV , did you get up and running yet? thanks for the well wishes and hope you get er going
 

·
Registered
Joined
·
10 Posts
Discussion Starter · #10 ·
Great! Glad you got it running. The intake I have on is a new Edelbrock Performer (Aluminum) for EGR engine. I could not imagine a leak under the intake affecting the engine (as FE andGoingBroke said) unless I also had a sealing problem between the heads and intake. Long shot, I know. I had used Edelbrock gaskets, but not their sealer, but similiar stuff. Thought I would loosen all intake bolts in reverse order, and re -torque. Then figured (faulty decision) to lift the intake just to take a look- well now I'm waiting for new Edelbrock gaskets and sealer from Jegs. My carb is new from Biggs, and was set up and run before they shipped it. Talked to them once, and their advice was to turn up the idle 1/2 -3/4 turn and idel mixture screw one turn out. Made no difference. I am using the stock EGR plate, but it is blocked at the flange for the EGR valve. (appearance only for state inspection) so I resealed this also. I'll talk to Biggs again, but went with them so I could bolt on a carb and have it ready to go. If there is a carb problem that I can't adjust out I am sure they will help. I'll find out what fuel pressure they want at the inlets also. I'll keep ya up to date. Thanks
 

·
Registered
Joined
·
448 Posts
You may also want to check all your mating surfaces for flatness too, I remember having a Ford EGR plate in my 351 that was warped to hell and as soon as I took it off the car ran OK , did you double check the ignition ? I did that little spark test on mine with a sparky and had spark right up till it died so at least I was able to rule that out. let me know what you find when you get it sorted out. that high starting RPM is normal cause ya just squirted gas into the motor form the accelerator pump. Good Luck
 

·
Registered
Joined
·
448 Posts
Forgot to tell ya Holleys can go up to at least 7PSI but after that your pushing yur luck, the float cant overcome the pressure and it wont close off the needle and seat,
 

·
Registered
Joined
·
10 Posts
Discussion Starter · #13 ·
I am up and running! I had put a manual oil pressure gauge in the port where there was an electric "switch" on the tee in back of the engine, along side the oil pressure switch (just for initial start) turns out this "switch" keeps the electric fuel pumps energized as long as it closes after a few seconds- via oil pressure!
Thanks for all the advice-and support- you all did make me feel better.
 
1 - 13 of 13 Posts
Top