Another hard start question, but different symptoms

[Fords4Us]

Hey all. This seems to be the month for hard-start questions. I have a similar situation, but with different details.

My 83 Ranger and I just went through the Duraspark conversion; we finished up in August and I've been driving the truck all over Creation since then. During that time, I've been fiddling with timing, idle mixture screw positions and idle speed, trying to get everything dialed in. Since then, I've come up with a combination that runs pretty well under most driving conditions, but now it's hard to start.

The starting issue is actually restricted to the first start of the day. The engine will crank for some time (about 5-10 seconds), then finally catch, then stall, then catch, then stall, then catch again. I've tried giving it no gas, or one tap on the gas pedal, or two taps of the gas pedal prior to turning the key, but it still takes awhile to catch under all three scenarios. Even after it catches, it's very finicky about how much gas it needs to keep it going. Too much or too little and it dies again. But here's the weird part: for the rest of the day, no matter how many times I stop and park and restart, the truck starts right up again very quickly and easily without any taps on the gas, and within a second of turning the key. It's only that first start of the day that is difficult.

Right now I'm running with the mixture a little richer and my idle a little higher than factory spec, but not by much. I've got the timing adjusted so that I have most of my power in the lower part of the rpm range (below about 3000rpm). Our outdoor temperatures haven't really been that cold yet, so I can't blame the hard starts on cold weather. I did notice that when this problem was at its worst, I was also having occasional, very small exhaust backfires when the engine was really under load. That made me think timing might be the issue. So I've been advancing the timing just a smidgen each day since this problem started. Those adjustments have helped a little but not really taken care of it.

I also read somewhere that a rich mixture combined with too little advance can cause hard starts, so I may try leaning it out a little in between timing changes. My only other idea is maybe the fuel filter is starting to get clogged, such that fuel flow is slower than it should be, and maybe it's just not enough at startup? Most of what I'm reading doesn't explain the discrepancy between hard first starts and easy subsequent starts, so I'm just not sure what to think at this point. Suggestions welcome. Thanks all.

 

[Spott]

The most obvious thing to check is the check valve in the fuel system. If it slowly leaks back, then you'll have no fuel up at the engine when you go to start it after sitting for several hours. It takes several seconds for the fuel pump to get any fuel up there. For shorter periods of time, it doesn't allow enough to leak back to starve the engine too much.

I don't know where your check valve is, or what to test for, but that's the first thing I'd look at.

 

[enjr44]

It's an 83 right? It's got a carb right? If not, none of the below makes any sense.

If so, it is probably one of two or three things. The choke is not setup correctly to start a cold engine. Fully closed, and then pulls off for a fast idle. Or the check valve in the manual fuel pump (on the engine someplace according to google) is leaking and pulling the fuel out of the carb's bowl. That is what mine was doing.

So, if you think the choke is working correctly, you have to see if there is fuel in the carb's bowl after it has set however long it takes for a hard start to develop.

Two ways to check it as far as I know. One way, after it has set take the top off the carb and look.

Another way would be to temporally replace the supply fuel line to the carb with a clear line and see if it gets empty as the truck sets. On mine you could see the fuel run out of the carb and back into the tank.

Or (maybe) pull the fuel inlet line to the pump from the tank and see if fuel runs out (not just a little; but, quite a bit) right after you shut it down. I don't think I would do this if it were me.

The third thing (and probably not) is a bad accelerator pump in the carb. When you cold start a carbed engine you usually have to pump the accelerator a couple of times to get enough fuel in the intake to fire it off. Because with a carb (unlike fuel injection), the air going into a running engine is what pulls the fuel out of the carb and into the engine. No air, no fuel. To check if its working, cycle the throttle while looking down into the carb. You should be able to see fuel squirting into the engine. Come to think on it, that is another way to check to see if there is fuel in the bowl, no squirt, not fuel.

 

[Fords4Us]

Thanks both of you for the ideas. I have some testing to do this weekend! I'll let you know what I find out...

 

[Big Jim M]

Done a lot of carb work in my time.. Backfire under load is caused by either too much timing (advanced) or to little fuel!
If you have hard early morning starts then first before turning the key give the pedal two or three complete floors to energize the small pump in the carb. If that doesn't do it for ya then adjust the choke.
What most folks don't know is the IDLE jets complement the hi-speed jet! So having the idle set too LEAN makes the high-speed fuel also too lean. Causing backfire under load.
I have never seen a carb that COULD backward drain the fuel out into the tank. All I have ever seen have the needle on the top of the carb and out of the fuel itself, so they cannot drain backward.
I suggest turning the idle mixture screws to a much richer mixture and then adjusting the fast idle screw back down. Most likely you have adjusted your carb into never-never land.
Big Jim

 

[enjr44]

I have never seen a carb that COULD backward drain the fuel out into the tank. All I have ever seen have the needle on the top of the carb and out of the fuel itself, so they cannot drain backward
Big Jim

Drop by the house and I will show you one, LOL. It is a Weber 32/36. The Holley 5200 is a licensed clone of that carb.
Ed

 

[Big Jim M]

Please explain

Drop by the house and I will show you one, LOL. It is a Weber 32/36. The Holley 5200 is a licensed clone of that carb.
Ed

According to all the natural laws I am familiar with backward draining from the Holly 5200 would be impossible.
The first thing a plumber learns is "shit don't run uphill"!
Here is a picture.

Big Jim

 

[enjr44]

According to all the natural laws I am familiar with backward draining from the Holly 5200 would be impossible.Here is a picture.

Big Jim

I don't understand it either; but, ain't going to shoot a vid to prove it. It isn't worth my time. And the bowl vent isn't plugged either. Just know without a great check valve it does it.