i searched and didn't really come up with much.

first crank of the day i can go out, one pump of the throttle, and the car fires right up. the starter barely hits.. it just catches so fast! once warmed up tho, i can shut it down and it will let out a massive back fire! usually shoots a 4 foot flame if i crank it back up immediately there is no issue... wait a few minutes or even an hour then i have to hold the throttle down half way or so and crank it over for about 20 seconds.

i have the fuel pump on a switch and lately i have been shutting the fuel pump off before i turn the car off. this has eliminated the massive backfire, but it's still hard to start when hot. The carb sits very close to the turbo (see pic for reference)... i now have a turbo blanket on the hotside but this hasn't seemed to help. i'm thinking this is a heat issue, but i don't know how to deal with it. i also have a 1" phenolic spacer under the carb.. no help.

one last thing to note.. after driving around a bit under full temp my idle gets erratic. it will hold an idle fine but it's sloppy as hell.. it just sounds very off. if i shut the fuel pump off for a second the idle will clear up a bit. i have checked the float level when this happens and it's still fine, just under the site plugs.

CSU 750: fuel pressure is 6psi base, referenced off the turbo. floats are a tad under the site plugs as per Kevin's request.

thanks as always fellas!

#ad

 

that combo just looks sick man......

1st yea that tubo might be heating up the fuel in the carb.. = hard start problems...
also check your timeing?where is it at start up? you know im have a simular problem hard to start when its warm but mine starts and puffs white smoke.but only sometimes its kind of weird.it might be a lean condition on start up i think that the fuel might be hot.but then anything is possable.jay

 

thanks man! it's a blast..

timing is at 0 degrees upon start up, which is where these things like to be. it hits only 8 degrees under full boost hahahaha. i'm really thinking lately that it's all because of the heat i need to block off the hood scoop since there is no top mount intercooler there anymore and raise the back of the hood maybe. try and get some of the hot air out.

 

I have had that problem for a while now. A high torque starter with a 875 CCA battery helped some but I still have to crank it for 15 seconds sometimes. I have had it where I have stalled it and it doesn't want to start at all. I installed a small air tank behind the seat for a test. What I wanted to see was if the carb was getting hot enouph to boil the gas out of the bowls. It would then be a sealed system because of the hat and intercooler. all of this would fill up with a very high mixture of vaporized fuel. There would be very little air in there just mainly fuel. That kind of mixture just doesn't like to fire well. I took the air tank and hooked it directly to the manifold and give it a 1/2 second blast of air and it would fire immidiately. Now if I installed a scoop directly over the carb then it may not get as hot and boil the gas as badly. I don't know any real way of preventing the gas from doing this. I guess try and keep the under hood temp as low as possible.

 

yea, i actually saw a thread where you talked about that. i'm hoping to do that as a last resort possibly... i did however find something about an hour ago. i pulled the front power valve to open up the pvcr's and noticed the gasket under it was doubled up. i took one out and it seems to idle smoother and so far it has started up without touching the gas pedal when warm. however, i have not gotten it super hot yet. i hope to do that in a little bit tonite

thank you guys for the suggestions so far. i'm mainly going to work on getting the under hood temps down as low as possible. i will post my findings as i go along.

 

The cars I've worked on that have start retards always started fine cold, and then are a pain in the ass hot, backfiring with the flame shooting out of the carb, etc. Have you tried throwing some timing in it @ hot start-up?

 

not yet, but i will give this a shot for sure. never really thought about that before but it's a good idea it's possible my timing is just too conservative for its own good lol

 

i do not know, good luck.

 

That gasket is supposed to be doubled up, I believe it has something to do with the spacing PV vs. pvcr's.

Looking at your pic, my turbo sits right infront of my carb just like yours. It will make a difference if you wrap your turbine with some sort of heat shield and put some header wrap around your downpipe. My carb also sits right over the "j-pipe"and the exhaust manifold, it's an inline six. I have done this to mine and it has made a difference, I can actually touch the carb after a run and I don't have hot start issues anymore. You might even look at a phenolic (sp?) spacer under your carb to displace more heat away from the carb. I don't think they make a 2-barrel phenolic for mine, but you could also use wood that has the same heat displacement properties, like in the old days. Jeg's sells all this for your 750DP. Even though I can still see fuel bubbling out of the squirter after I shut it off, it is better than what it was. Good luck.

Kirk

Kirk

 

yea i have a 1" phenolic spacer on there and the turbine is wrapped and shielded. i'm adding wrap to the downpipe this week and will be blocking off the hood scoop (in this car without the top mount i/c it once had the heat just hovers in that low pressure zone.)

i need some vents

 

Yeah, luckily this '73 bronco came stock with a pair of hood vents and then I ended up cutting out some of the inner fenderwell in the engine bay to get more heat out. My body lift helped, too.

Kirk

 

lol that's awesome! i'm gonna grab me another hood to practice on. not sure where the best spot/s would be to put some slits in the hood.

 

The bronco's are vents/slits are back by the windshield on both sides of the hood.

Kirk

 

thank you, i hope to get the new hood this weekend

 

This is also happening to my car... It fires up instantly if it has sat over night. But if I drive around a bit then stop and let it sit for a while, it cranks for like 10-15 sec before it fires up. Kinda a nuisance Anyone know what causes this?


Jeremy

 

well, i now have heat wrap on the downpipe, turbo blanket on the hotside, and have blocked off the hood scoop no help

my next attempt will be making a big aluminum blocking shield to hopefully block the carb from all turbo heat lol! it's going to look like pure ass but it may help. OH and still gotta put the other hood on with some vents >

 

So who else has this problem??? I wonder what is the cause? You think its too much heat?


Jeremy

 

My buddies car does the same thing and when it starts a big cloud of black smoke comes out I dont know if mine will do it it is still on jack stands as if thats unusual

 

I have also had this issue. I know for a fact that mine was due to fuel vapors filling the intake piping, displacing the air. After sitting for more than five minutes you could smell the gas wafting out of the air filter. I have been thinking about adding some sort of hot start valve to allow fresh air into the carb when cranking, kind of like CW25.

 

I have been trying to figure out where the fuel smell is comming from, now I know I dont see anyway around this problem do you guys? Makes sense the fuel smell seems strongest in front of the motor by the turbos.


What a PITA.


Jeremy