Tedd Thompson

I'm trying to address the problem of hard long grinding starts after setting for awhile.It seems others have had this problems with no definite cure or with mixed results. Alcohol/ gas evaporation may be part of the problem but I'm thinking most of this problem is caused by the fuel pump check valve going bad and allowing fuel to drain back into the tank causing a long delay before fuel can make it to the carb. I've epoxied the leaded casting plugs in the carburetor and found no help there so today I installed a inline check valve below the fuel pump and behind the add on fuel filter canister. After a few days I'll see if that helps with quicker starts and let you know if that's the problem or if not the search will go on.

Doubtful this is a fix but more of a diagnostic attempt. If it turns out the fuel pump check valve is bad a new rebuilt pump will be in order. Here is the inline check valve I used... Tedd https://www.amazon.com/dp/B01K9ZTGC8?psc=1

classicmuscle442

Great idea on check valve, just picked up a '56 and started it up after a long rest, been reading some of the info under vintage Oldsmobiles

ignachuck

I had long starting problems. Electric choke solved the problem.

WHIPOLDS

Tedd - thanks for posting your pursuit of the hard starting issue, I have the same problem with my 56. Frank I know the choke is part of the issue. Where did you get your electric choke and can you recommend what make it was.
Thanks
Rick

MDchanic

If all else fails, an electric fuel pump up in the frame rails, right by the tank, with a momentary push button under the dash will do it - hold the button down for a few seconds (until the sound changes) before starting, to fill the float bowl, and she should start right up.

- Eric

Tedd Thompson

No electric choke on my car, it's about a original as it can be and I don't think my problem is choke related. When I removed the fuel line almost no fuel was at the fuel filter canister, pump was dry as was the fuel line. The gas had to go some where and the only place it could have gone is back in the tank is my thought. If this check valve works it will show that the valve in the fuel pump is faulty and a rebuild is in order, I don't consider this a permanent fix but a way to eliminate and diagnose possible problems.

I'm going to let it sit all day and give it a good chance to leak down if it is going to, I should know by tonight..... Tedd

MDchanic

And the lines and hoses from the tank to the pump are all good, with no pinholes or cracks, right, Tedd?

- Eric

Tedd Thompson

I believe so Eric, I have not had it on a lift in a while but from what I can see laying on my back like a reptile, no rust is visible on the metal lines and the rubber lines have been replaced a few years ago and they still look good. I tightend all the clamps I could get to I'm going to give it a try in a little while, I'll get back after I give it a go.... Tedd

MDchanic

Good.

I'm not familiar with the First Generation fuel pumps, but a bad check valve in a fuel pump of that vintage does not seem unlikely.

Also, placing a functional secondary check valve before the pump would probably eliminate the need to fix the check valve inside the pump, if it were bad.
At the worst, you'd just need to install another external check valve after the pump to completely take over the functions of any bad internal valves.

- Eric

ignachuck

Rick, it's a Tomco #9298 choke thermostat for the Rochester 4bbl... I don't remember where I got it, but somehow I think it was off the rack from NAPA

ignachuck

Tedd, does that mean you put the vacuum wipers back on?

Tedd Thompson

[QUOignachuck;974995]Tedd, does that mean you put the vacuum wipers ack on? [/QUOTE]

Not me! love the electric wipers but I still run the original fuel pump though it has been rebuilt sometime around 2001 or so.

WELL... I started it up tonight and it fired up after seven rotations of the starter..... Not bad but not what I was expecting. I hoped It would fire on the second or third go around but that didn't happen. So the jury is still out, I think I need to leave it a couple three days and see if it still starts on or about seven rotations or continues to crank fifteen or eighteen times like before till it fires.Time will tell if it's a fix or not ...... Update sometime around Wednesday.... Tedd=

redoldsman

I know the electric fuel pump is always a controversial issue and I seem to remember you do not want one. I have one on my 54 and it does not have the starting issues. Unlike what Eric mentioned which is a pretty good idea, mine is the only fuel pump I have. With the way my AC brackets are mounted, I cannot run a regular pump.

Ozzie

All seems to be on track for a resolution. I thought that I'd just add a few comments. The original pump depends on two one-way valves to pump. If the fuel is siphoning back into the tank, both of the valves must be leaking (assuming no other leaks anywhere). This is possible. If the added check valve is functioning correctly, such should be revealed. Another way to check the pump is to disconnect the discharge line and apply a bit of pressure with a hand pump or blow through a hose. If it will not hold pressure both valves are leaking and should be replaced. Pump efficiency will be significantly improved by this also. Figure 8-67 shows the valves. When replacing them, be sure to check the new valves. New doesn't always mean "good". Performance verification of new parts should always be done when possible. Also be sure that the valves' gaskets are in place and are not leaking. Keeping everything "fuel tight" is always a bit of a challenge. I hope that we get a report on the outcome.

P.S. When I was using an automatic choke the originally stated problem was aggravated when the choke would not close completely on a cold start. Changing to a manual choke helped and assured complete opening with the engine at normal operating temperature, with complete closure when cold.

WHIPOLDS

Thanks Frank!


To all -
I have a question. My Carburetor is labeled GM 4Jet - My parts car had a carb marked Rochester 4GC. Are these the same carburetors? Which should be original to the car.
Rick

Tedd Thompson

Same carburetor different names, but there are a bunch of 4GC's/4 jet's that have minor differences so it's not a one size fits all thing. When ordering kits or parts you should order by the carb tag number if your carb still has one... Tedd

WHIPOLDS

Thanks Tedd!
Rick

Rocketowner

A $35 Electric pump from Auto Zone and a lighted switch certainly solved this problem for me,as Eric already stated. I was concerned mine was going to wear the starter out.I only turned it on for maybe 10-15 seconds and turned it off after it started ,so it ran on the original pump. Problem solved ,and if your old pump went out on you ,the electric was a good backup that would get you home. Larry

47 Convertible

________________________________________________

This is exactly what I did with the 455 in my 47 Convertible. QJet was rebuilt by Cliff so am pretty sure all was done correctly. A 'new' mechanical pump as well. But it was still a long grind and a lot of foot feed pumping to get a start after it sat for more than a few days.

I have a remote switch that operates the electric fuel pump which is back close to the tank. Click it on and let it run until you hear a different sound, shut it off and pump the foot feed a couple of times and it starts right up. After that the mechanical pump seems to handle fuel transfer chores just fine. This suggests to me that fuel is reverse siphoning back to the tank. (Maybe poor venting at gas cap?)

Back in the day (50s and 60s) it was pretty typical that a start up after prolonged sitting time involved turning on the key, pump the pedal several times, engage starter and if it didn't start keep pumping the pedal until you could hear it trying to fire. I worked at a used car lot during Jr. College as a 'lot boy' detailing the trade in cars and doing mechanical work and it was thought normal for a car to take a while to start. Among my duties was starting each car on the lot and letting it run a few minutes at least twice a week. It also kept battery charged. Chokes were either manual or worked on a heat riser (so-called automatic chokes) but were thought to be necessary only for cold weather starts. Didn't seem to make any difference what make of car, they were all hard starting after sitting for days in between starts.
I see Larry has the same fix. Great minds must think alike
Jerry

Tedd Thompson

All good ideas above but if I go back to showing the car seriously again the fewer changes made the better the score or less work to get it back as close to original again... It's a **** thing and not necessarily a good thing, but it's the game I play sometimes..... Tedd

DFitz

My '55 also takes a while to get started after a lay off. It usually isn't a problem, I have a rebuilt starter from a few years ago, and it seems like it cranks just fine.


We have to remember, as alluded to a post above these cars are not the modern fuel injected instant start cars of today. First, dumping raw fuel into the intake manifold will take a few revolutions to get to the intake valves, then atomize enough to become a combustible mixture. Maybe 30s to a minute of cranking total.


Even if the fuel pump check valves are working, gasoline is a volatile fluid and will evaporate fairly quickly and may take a few more revolutions to get the carb filled and going again.


After my car fires, and is hot. I can usually just bump the starter and it goes. So there is some kind of fuel recency issue going on. What the cause is, could be check valves, but my guess is that we have just forgotten what these cars were like way back when. I have a couple of other carb cars and they too take a while to crank after a layoff.


Back when these cars were new, they were daily drivers. A long layoff was unusual so this issue may not have come to light very often.


I could be off base, but I don't worry too much about my car. If installing a check valve helps, that's an easy fix. Looking forward to the results.

ignachuck

X2 what Tedd just said ^^

cmpcpro

I had the same issue. I thought maybe the fuel was draining back out of the carb, or something along those lines. Ended up being the choke. After finally dialing it in it fires right up now.

Tedd Thompson

Well it fired up after eight rotations of the starter. Better than anytime in the last year for a three day set but not what I had hoped for.The car started after that in one or two rotations just like a real car does. I find it hard to believe that all the gas evaporated out of the carb bowl in this cold of weather but maybe it did....

On to other issues, top won't go up the last time i tried to put it away, I'm looking for a leak or a reason the pump ran out of fluid... It never ends.... Tedd

DFitz

That's funny!

classicmuscle442

Disappointment leads to excitement when we fix them.

ignachuck

Excellent point. That's why a lot of us nuts are wrestling with these old cars on a daily basis.

WHIPOLDS

Tedd - Did you install two check valves? Just wanted to clarify one below fuel pump and one below filter. My add on filter is above fuel pump. I got the check valves from Amazon. Arrow points toward carb right?
Thanks
Rick

Tedd Thompson

Only one check valve and it is below the fuel pump on the inlet hose next to a add on fuel filter I put on last year.

Maybe I'm missing something here but why would I need a second check valve above the fuel pump? Gas can only escape one way and that is through the fuel pump and down the gas line to the tank. This check valve should stop this from happening. Or a'm I over thinking this .... Tedd

WHIPOLDS

Tedd - Thanks, you were not over thinking this, I was. I was thinking the valve below the carb would keep the carb full as a back up to the one below the pump. The one below the pump should do the trick then. I will let you know if it helps my starting issue.
Rick

MDchanic

To duplicate the action of the two check valves inside the pump, if you believed that both had failed.

One prevents pushing fuel backward into the tank during the "push" phase, and the other prevents sucking gas out of the carburetor during the "pull" phase.

- Eric

Tedd Thompson

If both valves fail there will be no suck blow action and as we all know everything stops at that point.... Tedd