Fuel problems with Chrysler 75 Circa 1986

Hi all. I have used this site to solve many queries / ensure what I think I know is also believed to be true by others. Thank you for that.
OK. I have a Circa 1986 75hp Chrysler outboard that will not draw fuel. The tank and lines to the pump are new. The lines to the carbs are new. The filter is clear and pumping the priming bulb pushes fuel out at the carbs with the line disconnected.
I removed the carbs and cleaned them. That is i rinsed them in clean fuel, checked the float valves and replaced them. I did not touch the jets.
On reassembling the engine fired and ran for 10 seconds. It then did not start until easy start was sprayed directly into the carbs. I know, not my engine and not my idea. I hate the stuff!

Holding my hand over the carbs with, the intake cowling removed, pulled fuel through and the engine ran for 30 seconds.

I have a feeling the fuel / oil mixture is far too rich. Could this make enough difference to prevent fuel flowing freely?

I plan to take the carbs off tomorrow and strip them fully, all needles out etc to ensure they are clean as the engine has not run for six months plus and the fuel in the bowls was very oily.

basically.... Is there something I am missing?? Like a fuel cut off switch?? I dont have a compression tester, but the engine has run well before all this. There is great suction at the carbs so I think the reed valves etc are OK

Oh yes. There is a great spark. I have replaced the CDI box with coil/condenser and gap type plugs. The plugs stay dry. I am convinced it is fuel starvation. The easy start sort of proved it and when I forced fuel to be sucked through it ran well enough. The carbs do need adjusted, all fuel lines are secured with cable ties and the primer bulb gets good pressure.

All help / comments welcomed.

Dave

Re: Fuel problems with Chrysler 75 Circa 1986

Have you checked the fuelpump diaphragma and the checkvalves?

Re: Fuel problems with Chrysler 75 Circa 1986

Thanks for the reply.

In short, no! I am planning to disconnect the fuel line and see if it pumps fuel when turning over. If the carbs are full by the primer bulb surely the engine will start and run till they empty??

Where are the check valves? are they in the pump?

Re: Fuel problems with Chrysler 75 Circa 1986

Ok. So I stripped and rebuilt the carbs. They are straightforward so am confident that they are clean and sound. Idle screws set to 1 and 1/4 out. A hand over the carb causes plenty of fuel to be sucked through and got the engine running for approx 1 minute. There was still fuel in the bowls when it stopped, so am also confident the pump is pumping well. The float valves are 100% under pressure and vacuum. It stopped with a massive backfire so I checked the timing. 30* BTDC is where it is set on the top cylinder. That is, at 30* there is full voltage at the distributor side terminal. I don't know what the dwell angle should be. It still appears that there is no fuel at the cylinders. The plugs are dry after prolonged cranking and when removed there is no sign of fuel being expelled.
I am at a real loss on this one. I now doubt the timing and keep thinking there is a problem with the fuel. The fuel lines are new as is the fuel. Either way it is not getting through into the cylinders. Removing the reed valves is too much to do in a friends backyard.
ALL ideas are welcome at this stage as is info on how to set up the distributor and points do it should at least fire. There is an excellent, strong spark. Thank you.

Re: Fuel problems with Chrysler 75 Circa 1986

Couple of things: The engine will starve for fuel and stall well before rhe carbs go empty. If it is a Chrysler, it is before 86, by 1986 they were Force. If it is badged Chrysler and had Prestolite electronic ignition it would be most likely between 1979 and 1984.

When you rebuilt the carbs, Did you clean out the idle system? You need to run a pipe cleaner or small diameter wire up the brass idle tube. That is the thin tube that runs to the top of the carb. You must also remove the low speed needle and spray cleaner--I like WD40--through the tube and needle. Be certain that it squirts out the small holes in the rear on top of the butterfly. It should also squirt out the bottom of the small brass tube. Floats should be set to level with the casting with the carb inverted. With the carbs upright, you should be able to blow through the needle with little restriction even though the hole is less than 1/16 inch.

Understand: When you try to start the engine, fuel is delivered by the low speed system exclusively. The main venturi does not deliver fuel until about 1/2 to 3/4 throttle. When you choke the engine OR hold your hand over the carbs, THEN, fuel is deliverd by the high speed dip tube (the thick brass tube that only extends about half way into the carb venturi.) Additionally, it can draw from a lower fuel level in the bowl. THUS, your problem is likely the low speed fuel delivery circuit or lack of fuel to the carbs.

Go back and re-clean the carb low speed circuit. Change the fuel pump diaphragm and gasket if you have not already done so. Examine the check valves in the pump by trying to blow and suck through them. They should open easily under pressure and close--not necessarily air or liquid tight, but there should be some resistance-- under vacuum. Check valves are the three brass circular things inside the pump. The center one is held in by two screws.

The distributor is set by putting the engine at top dead center. The top pulley should be set with the circular line matching the curve of the flywheel and the straight line pointing directly at it. Points are set at .014 open on a high lobe and the distributor is adjusted to 32 or 30 degrees befoer top dead center at wide open throttle. Search out other posts on distributors for more detailed instructions.

Re: Fuel problems with Chrysler 75 Circa 1986

Excellent info. Thank you. I will double check the carbs. It does make sense that the low speed jets are not delivering fuel. The outboard IS Chrysler. The dates are my (mistaken) guess. The distributor timing marks are as described. Although it looks like there was a 'sticker' showing the timing marks on the flywheel it is gone. However, there is a faint 'o' and someone has marked the flywheel as one would do when using a strobe.
I now look forward to a Sunday afternoon of petrol and WD40!
Thank you again.

Re: Fuel problems with Chrysler 75 Circa 1986

When you cleaned the carbs,how dirty were they?

Never assume that something is good?
Physically check the diaphram.
It could have a pin hole or a tear.

Backfiring,could destroy it and the reeds.

To check the reeds,take the carbs off and look inside.
You don't need to take them out to do a check.

Re: Fuel problems with Chrysler 75 Circa 1986

The carbs were actually very clean. No varnish and no deposits. The idle jets were also clean and in reasonable shape. The pump is going to be examined today and will take a good look at the reed valves when the carbs are off. I am well used to disassembling carbs from small two stroke engines (chain saws, strimmers etc) which have diaphragms and tiny springs etc. These carbs are much simpler devices (although probably just as particular about dirt and settings) or am I missing something.
Thank you again for the input. 14.30 on Sunday afternoon here so I should get started!

Re: Fuel problems with Chrysler 75 Circa 1986

The jets could have a tiny amount of anything clogging them.
I use an accetelene torch tip cleaner.
I use soap and water then blow with air to dry.
You can use anything to clean them.
I just use soap and water to remove the film some cleaners leave.

Yea they can be a bummer.
I cleaned one carb 3 times before it finnaly was right.