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302 Pops and trys to die at top end ( was "newly overhauled 302 won't start".)

N

Neal Franson

Regular Contributor
Well, I put in a new fuel pump. fuel filter and had changed the anti-siphon valve to an oversized one, new fuel line and blew out the fuel feed into the tank, all 3/8", including the fittings, took it to the ocean, and it did the same thing. After full throttle applied, it took several minutes, maybe 5 -7 minutes before it started popping and almost died, until I eased the throttle. I did try it again a few minutes later and it did the same thing after about a minute. The pops are muffled, like going through the exhausty, not the carb.
I did a pressure and volume test on the fuel pump before I went out and it was better, the pressure was about 3 1/4 pounds ( was 2 1/2 on the old fuel pump.) The volume test wasn't quite standard, but it filled the pint jar with a couple of 15 second turns of the starter (supposed to do it in 20 seconds at idle.) (And I still have the slow to start.) The old pump was about 1/10th of a pint, a major fail.
So it sounds like a fuel restriction, but everything is new and oversized. I'm am not sure why the fuel pressure is a bit low, it is supposed to be between 3 1/2 and 5 pounds, but is just under 3 1/2. This is my second new fuel pump. I can do the tests again.
It runs well up to at least 3000 rpm. The gas is mainly very new with marine Stabil. The gas tank is stainless steel and was cleaned out about a year ago and the gas looks clean when I took out the fuel sender and blew out the feeder line.
I did rebuild the carburator, but may need adjustments. I did try to keep all the connections tight along the fuel line so I don't think there is an air leak.
Then I still have a problem of it not starting right away, hot or cold - takes a while for it to hit. When the engine is warm, I know now to leave the throttle pretty high and not pump it, as the heat can cause the gas to boil in the carb and flow into the intake manifold, causing a rich mixture. But this didn't solve it today, at a critical moment it still didn't start and the wind blew me into the dock.
When it is cold new start, I usually pump the throttle a few times and then leave the throttle on pretty high, which worked well today at the marina, but not reliably, as it didn't work when I got home and flushed out the salt water - took a little while.
 
Based on your description, I'd say you have two issues - the starting issue and the pops/dies after running issue.

the testing you described sounds like a static single point test...that is fine when things are normal but I'd say you are not in that arena at this point. I would suggest 'tee-ing' in the vacuum gauge to the suction side of the fuel pump and watching the vacuum level as the engine runs and the load is applied until the pop/dies occurs. It is the simplest way I know of the get a decent understanding of what's going on with fuel delivery.

the starting issues may be the carb adjustment(s) and or the initial timing value...I would defer that one until the pop/dies issue is resolved - that one suggests a very lean condition which is not good for your fresh engine and will damage it over time...just my thoughts...
 
So, if it needs to be done under load, I have to take it back to the marina to do this test near full open throttle with the vacuum gauge hooked up in the line with a tee. Can it be before the fuel filter? It is going to be hard to get a tee in there anywhere else. What values should I look for?
 
In more than one case, I've removed the hose from the pump and inserted the Tee into that hose. a short piece of hose and a couple of clamps connects the
Tee with the pump and then the vacuum gauge goes into the third leg of the Tee. Ideally, the gauge should connect to the suction side of the fuel pump. What should you see - ideally, less than 1" Hg...that said, anything under 4"Hg at cruising RPM is usually adequate. WOT is a nice data point but really not essential.

A qualitative option exists if you thing the vacuum gauge is too much trouble - just bring an outboard tank. remove and plug the hose from the onboard tank...and then connect the outboard tank to provide the fuel to the pump. If the problem goes away, you know its the fuel system before the pump where the issue is...
 
Not much. I took out the fuel filter and it looked good. The connections from the fuel filter to the fuel pump are tough. There are 5 threaded fittings attaching the line to the fuel pump, and no barbed fittings and no hose clamps, and not much room. I tried undoing the top connection and the line started to twist, so I twisted it back tight. I connected the hose to the fuel pump between the 2ed and third connection from the pump, which is a pressure fitting like a natural gas connection. I may have to take it apart there and get several connectors to make it work.
I didn't tell you about the other problem that I have been working on. I came back from the marina with only three tires, wheels, and hubs. I never knew until I got home. It doesn't help that I don't hear that well. They must be on the freeway some place. No one honked at me, or anything. The spindle was also destroyed, so I have been trying to get it off, without success, yet. The parts will be here later in the week, so will try to get that finished up next weekend, but probably won't make it to the marina.
What do you think about octane? Would it help to put some high octane gas in, plus I have another bottle of octane booster? I am also a bit perplexed on what to do if it is a good or bad reading. I do have an in-line fuel pump that could perhaps be utilized.
 
This is the idea with the in-line pump: Install it just before the fuel filter, and switch it on from the dash when I want to floor it. It would be much simpler than installing a T for the test, and this may be an actual handling. It would be like switching on the overdrive. I will have to see if it creates resistance when it is off, I think not. It could also be connected to the ignition. I understand it wouldn't necessarily handle the problem I have, but may bypass it and act as a test, as if it doesn't handle the problem, we can be pretty sure it is not a fuel supply problem and may be more carburation. It would be easy to switch back, as well.
That and increase the octane.
 
"pressure fitting" and "natural gas connection" are ambiguous, at least to me...what, exactly, do you have for fuel line and connections
between the tank and fuel pump?

Bummer on loosing the wheel....last couple of failures as you described that I was asked to look at received replacement axles...depending on what you have, especially if its old, you may wanna consider...

On you 'in-line' pump concept, I was taught "one fuel pump on a carburated engine"....injected systems are a different breed. as far as powering an electric fuel pump, you will need a 'safety switch' to ensure the pump is turned off whenever the engine is not running...Most use one of the versions of an oil pressure switch. Of course, this is for permanent installations - you can do what you want for troubleshooting purposes. Honestly, I'm thinking an outboard tank would be easier for troubleshooting than the electric pump...

On the octane booster - it won't hurt anything but your wallet...your description suggests you have insufficient fuel, not fuel with inadequate octane...
 
I have some extra fuel line. If you think this is a problem, I could just put some 3/8 barbed connections and a couple of hose clamps with some marine fuel line, and call it a day. It doesn't leak, but may flow better that way. Then I can easily get the T in to do your test.
The axle replacement is a good idea - certainly easier than replacing the spindle. I already have the parts on the way, so we will see how I do.
 
I can't say if it is a potential problem or not - never seen what you have described. that said, fewer fittings = fewer restrictions = less pressure drop...
 
Yes, I had to order a new axle, as the damaged spindle would not come out leaving something that I could weld back together with any confidence. I also got two new aluminum wheels and two new load level E (10 ply) tires. One new wheel wouldn't match, so I got two and used the other odd old one for a spare, which I didn't have.
I did change the fuel line and connections from the fuel filter to the pump. The fuel filter and fuel pump actually have 5/16s NPT holes, but had these square type Ls that increase to 3/8", so everything is not 3/8s, as I thought. But the connections are cleaner. I have't done the tests, as I couldn't get it started, which seems it isn't getting any gas, as I got some pops from starter fluid, nothing otherwise. The pump should suck the gas into the carb without priming the pump, right? I need to check it out further and make sure there is gas in the filter, etc. Hopefully tomorrow, weather permitting. I also ordered a 3 gallon portable tank and connections, which I can also use as reserve fuel.
 
No surprise on the axle....at least that and the spare can be checked off of the list...:)

I think you are correct in that you don't have enough fuel in the carb to start it...yet. The pump should purge the air but may take several tries before it is successful...with today's blends of gasoline, its pretty common to have the carb bowl empty out, due to evaporation, after a week or two. I know more than one individual that resorted to a squirt bottle (like a small ketchup bottle but with a U shape nozzle) to add a few ounces to the carb's bowl after the engine sat dormant for a while....just don't store it on the boat.

Not sure what 'connections' you have to make use of the portable tank as a reserve source... I'd be hesitant to have that be permanent...
 
Just to get it hooked up for the test, I need connections, as I don't have the outboard connectors that the tanks have. I ordered a new 3/8" line and primer bulb, tank feed as well as some brass fittings, as the outbord connections are just 1/4". I was planning on storing it in the cuddy cabin in case I ran out of gas. Is that a bad idea?
I mainly worked on taking off the old axle today, didn't get any farther.
 
I think I found my problem with the high end cut-outs! After fixing up the connections around the fuel pump and filter, it wouldn't start and I found it wasn't getting any gas, even to the fuel filter. I had an extra 3/8" priming bulb, so I discconected the fuel line from the fuel filter and put the bulb there and after a few squeezes, I had fuel. I hooked this up to the fuel filter and pumped, and gas was leaking out of the top of the fuel filter, so in the vacuum created by the fuel pump, it would have been taking in air! I tightened it as much as I could and it still leaked, so I took it apart and put another old gasket in the fuel filter and tightened it way up and it held. The engine started right up!
I was then going to do the fuel pressure and volume tests, but I needed the engine to start quickly, so I shut it off and ran into my other problem of it popping once and then just grinding with no pops and no starting. I couldn't get it to start again. I experimented with this a bit. It was not even fully warmed up, so it wasn't gas boiling into the intake manifold. If I pumped the gas hard and left it pretty full throttle, I started to get some pops. I kept this up and got it started again - a lot of throttle pumping! I shut it off and did it again and it took a few trys, but it started again. I shut it off and did it again, but the battery was starting to run down at that point, so I had to give it up.
It seems to need more gas than it is getting when starting. It is still idling high at 900 rpm or so. I can't slow it down, as the linkage is bottomed-out, the idle screw is backed way out so I am not getting any advantage from the low speed compensation of the carburator. The only way I can slow down the idle is with the idle mixture screws, but that is counter-intuitive. You are supposed to adjust them to highest speed, and the turn back the idle screw, which I can't do, to my knowledge. There may be some other linkage adjustment - I'll check it out.
Still waiting on the axle.
 
I seem to remember you have the initial timing set on the higher end....may want to reduce the timing to 8-10 deg BTDC...
 
I assume reducing the timing advance is a possible solution for the starting problem. I set it at the highest vacuum reading, which was 14.
It started pretty quick the first time I started it today, but slow after that, and still started best with pumping the throttle and crank at high throttle. Maybe that is best for the 14 degree advance - I can see why that may make it harder to start. I will adjust it to 10 and try starting it. It may handle my high Idle speed as well.
I did take a reading on the fuel pump pressure to the carb, and it was better at almost 4 lbs. My gauge now zeros out at minus 2 lbs for some reason, so that may be a 6 lb reading. I think we solved the high end cutting out by fixing the air leak at the fuel filter. I did get the 3 gallon tank that I will take with me next time out, in case it still cuts out.
The axle came and I welded the tabs for the spring seat, and got it all installed except for one of the tires was a bit tight to get to, and I ran out of daylight.
To pass my sea trials, I want it to go full throttle for at least and hour or two, I want it to start reliably, and everything working with no other random problems. So the major one now is starting reliably. I may not get to anything else until next weekend. If I get it all together and the starting handled on Saturday, I may take it out on Sunday.
 
Sounds like some progress...I know its hard when you have a handful of issues...

On the sea trial, let me caution you against sustained full throttle operation...you will take a lot of life out of the engine doing that for two hours...I would suggest sustained operation at no more than 75-80% of full throttle (WOT) rated RPM...your WOT value is probably higher given the mods but I wouldn't encourage full rated RPM for more than a minute - usually just enough to know that things are still 'right'.

My thought was reducing the timing would slow the engine, perhaps enough to operate it solely on the idle circuit of the carb, especially if the stop screw is backed out and the throttle plates are closed (as far as the design allows)...it should also make starting easier and quicker.

And don't forget to make sure the alternator is working before you venture too far out...nothing worse than 'running out of battery' and losing spark with nothing but ocean meeting sky at the horizon...
 
Okay, I didn't realize that about FOT. A minute??? I did put those stops on the distributer that keeps the engine from going too fast. That wake spewing out the back at 38 knots is so incredible.
I do my sea trials behind the breakwater at San Pedro. I also have towing insurance. I also have solar panels. I wouldn't know what to do with the alturnator other than pat it on the head and say "Good alturnator!"
 
The 'stops' in the distributor only control the ignition timing, not the engine's operating RPM...

As far as the alternator goes, just make sure it is charging the battery while the engine is running...I recall early on in your saga there was some wiring to/from the alternator that wasn't 'correct'....just wanted to make sure it didn't slide off the plate...
 
Yeah, we changed the wiring from the aturnator to go directly to the battery, through the batt side of the selonoid, instead of going up through the ignition switch and back down to the selonoid. That was one of your first recomendations. I also put a 40 amp fuse on that line.
So I will just make sure the volt meter is reading 12-14 volts. and pat the alturnator on the head.
 
Being kind to the alternator is always a good thing...

voltage out, with the engine running, should be at least 13.8 VDC, not more than 14.5 VDC.
 
Just remember your electric shift "fossil drive" draws constant electicity for ignition & FWD gear, a small amount for engine instruments plus blower/bilge pump. If battery gets too low, even if you still have ignition you may default into neutral & go nowhere.
 
Adjusting the timing to 10 degrees BTC (from 14) handled the fast idle problem, but still starts poorly. If I get an initial hit on starting, it takes pumping the throttle like crazy to get it to start. What I want it to do, is when I shut it down at idle, to start again immediately at the same settings. Why wouldn't it??? It almost did that once, I got an initial hit, but I still had to pump the throttle to get it started. If it gets into grinding with no hits, I usually have to wait a few minutes to get an initial pop, and then pump the throttle to get it started. If I don't get an initial hit, it just grinds and won't usually hit again. I have to stop and try it again to see if I can get an initial pop. I did try it lower than 10 degrees, and it just lowered the idle, but didn't improve the starting. I also tried various settings with the choke, but had little effect on anything. The motor was not very warmed up, just running off and on every few minutes. Does anyone have any ideas on this?
 
I would say you need to investigate the starting issue further...sounds like you are on the Air/Fuel path....but you need to make sure there is a good spark while cranking.

how slow did you get the idle down to? did you check the idle mixture adjustments after resetting the idle?
 
I did rebuild the carburator
Reading through all this, this hits me square in the eye. Every performance issue you have...hard starting, having to advance the timing to get it to run, popping, etc. points to an extreme lean condition. What carb is on there? The other question I have is whether it has points ignition or something else. The issues you describe can also be laid at the feet of a bad condenser.
 
I switched to a Pentronix electric ignition, so no condenser. It has the Holley 2 barrel stock carburator. I do have a Chinese knock-off of an Edlebrock 1409 4 barrel that I could put back on, but I did had a problem with it. It is 600 cfm instead of the 500. It also has bigger jets on the primaries. The aluminum intake manifold that I put on seems to have much more internal volume that the steel one, that I still have, but it had a scar on the flat surface where the gasket goes, so the re-builder said to get a new one. I may be able to weld and grind that smooth and put it back on.
I have had excellent spark with the Pentronix electronic ignition, it's accompanying Pentronix 45,000 volt coil and the iridium spark plugs. I got the idle down to 400 and then it died. I left it about 500 - 550. Yes, I should re-check the lean mixture adjustment to the highest vacuum reading and then re-set the idle if needed and check it again. I'll do that today.
 
Success! Or what looks like it. I adjusted the idle adjusting needles - couldn't really tell much of a difference on the vacuum gauge, so I just adjusted them up a bit and stayed where it was running best, readjusted the idle and turned the engine off. I did nothing but turn the switch and it started right up at the idle speed. I did it again five times and it started right up at idle. I then did a few other projects and did the same thing 45 minutes later and it started right up at idle! No pumping, just a key turn - that is what I was going for. We'll see if it holds up.
I did finish off the axle, but need some spacers to center the tires in the wheel well so that they don't rub, which I am waiting to be delivered on Wednesday. Looks like next Sunday for sea trials!
Thanks to everyone!!!
 
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