When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I got a project I want to work on today.
If my car sits more than 2-3 days it takes a few start attempts to get fired up.
Try #1 - crank about 5-10 sec.
Try #2 - crank about 5-10 sec.
Try #3 - sometimes finally gets gas and fires.
if cars sit 1 day or less it fires right up.
Anyhow, looking for diagnostic tests I could do?
I plan to pull fuel line at inlet and see if it has gas or if it’s draining back to pump.
any easy way to check if fuel is still inside carb? Or if it’s draining out back through pump?
You should see fuel squirt into the venturi of the carburetor from the accelerator pump. If you don't see the fuel you know you're loosing it somewhere.
You can measure the float height through the bowl vent. Kent-Moore and Buroughs both made calibrated measuring sticks for this, but you can do the same with any lightweight stick. A coffee stir stick is about right. With the engine running, place the stick in the bowl vent and mark where the float sits. Now come back a day or two later, drop the stick into the vent, and note where the prior mark was. A significant drop in float level indicates that you either have a drainback issue or an evaporation issue.
Thanks Joe, cool carb tool gauge. I don’t have one but I do have a thin wooden coffee stirrer. I’ll run that test after my Sunday cruise.
Also, thanks for location of vent hole, I didn’t know where that was.
I’ll also try the squirt test Olds mentioned.
i guess since car has been sitting a couple of days I could also run test in reverse? Check height now and then see if it’s higher after drive.
Do my symptoms kinda sound like a carb fuel drain issue?
Last edited by mb13; March 31st, 2024 at 08:11 AM.
Thanks Joe, cool carb tool gauge. I don’t have one but I do have a thin wooden coffee stirrer. I’ll run that test after my Sunday cruise.
Also, thanks for location of vent hole, I didn’t know where that was.
I’ll also try the squirt test Olds mentioned.
i guess since car has been sitting a couple of days I could also run test in reverse? Check height now and then see if it’s higher after drive.
Do my symptoms kinda sound like a carb fuel drain issue?
Could be fuel drainback or evap. I find that pretty much all of my carb vehicles that sit for a while take longer to start. We're all spoiled by EFI and pressurized systems with a self-priming electric pump in the tank. I usually use a couple of extra pumps of the accelerator before starting.
My starting procedure is turn key and crank for 10-15 seconds, stop and pump the pedal 2-3 times, repeat cranking and pedal pumping 2 or 3 more times until the engine fires. If the car has sat for a long time, it takes more cranking than that and the oil pressure gauge jumps up before the engine fires. I sometimes pour a bit of fuel into the float bowl vent to get the engine to fire faster.
I don’t mind a little work to get her started after a couple of days…Fun’s start procedure sounds just fine to me. But, mine takes 3 versions of Fun’s version which seems a tad excessive. Not crazy but I think it could be better.
anyhow, I just did a couple of quick tests per Joes post, I’ll try multi-day test starting tomorrow.
So, cars been off 1 full day, measured float. Then started car, ran for a minute, turned off and measured float. It was up 1/8”-3/16”. Like I said I’ll try test in reverse for multi-days starting tonight through tuesdayish.
Also, I temporarily installed a see thru filter at supply line to pump, kinda weak pressure only fills filter about 1/4 of the way, but I’ve heard that’s normal.
lastly I propped up see through filter horizontal to see if there is any drain back towards tank, and so far I see none.
Separate issue….Car was dying with temporary inline fuel filter, so I removed it. Now is fine. Seems weird pump can’t suck enough pressure through it, maybe filter was a tiny bit dirty or something.
Anyhow, back to the float…when I first came into shop with cold car sitting for a day. Also tried Olds’s squirt test. I got one solid squirt, then for the hell of it I gave it another hit and only got about 1/2 a squirt, then third no squirt….hmmm
The rubber supply hose to the fuel pump can be temporarily pinched closed as a test for drain back if the fuel bowl level falls. Sniff the crankcase oil for gasoline.
Fun’s start procedure sounds just fine to me. But, mine takes 3 versions of Fun’s version which seems a tad excessive.
To be clear, I typically do 3+ cycles of cranking for 10-15 seconds; sometimes as many as 6 before the engine fires. I just crank and pump until it starts.
The rubber supply hose to the fuel pump can be temporarily pinched closed as a test for drain back if the fuel bowl level falls. Sniff the crankcase oil for gasoline.
I’ll try that test too…I’m starting to think it may be leaking out bottom of carb. Welp, seems I just ran her out gas….kinda a comedy of errors in shop today.
At least I got a new carb level tool, almost as cool as Joe’s
To be clear, I typically do 3+ cycles of cranking for 10-15 seconds; sometimes as many as 6 before the engine fires. I just crank and pump until it starts.
sounds just like mine. I mis-understood ya.
maybe mines ok as-is. Trust me I’m not spoiled with my F.I. Cars….i also have old jeeps, so they start awful also.
Joe, you mentioned significant drop…do you know how many 32nds or mm is considered a big drop.
just in my initial test I’ve already notice about 3/16” difference between low level and high level.
You’ve “heard it” but has anyone actually documented that was the issue with their carburetor? As Joe P has posted many times, it was an issue with the early carbs that used press in plugs, and was resolved with the spun in plugs, but has been perpetuated as an internet myth. If you find yours are actually leaking, post pictures and data to confirm that is the issue.
As said in earlier posts, you and I have the exact same issue, and I know my well plugs do not leak.
Last edited by Fun71; March 31st, 2024 at 05:31 PM.
You’ve “heard it” but has anyone actually documented that was the issue with their carburetor?
In half a century of rebuilding Qjets, I've found leaking plugs exactly one time - on the original carb in my 1967 Delta, which of course is one of the early carbs with the sheet metal plugs that DO leak. Anything with the spun-in aluminum plugs (pretty much 1968-up) will be fine.
I don’t mind a little work to get her started after a couple of days…Fun’s start procedure sounds just fine to me. But, mine takes 3 versions of Fun’s version which seems a tad excessive. Not crazy but I think it could be better
Have you read the owners manual to see how to properly start your car ?
My Wifes Riviera is exactly the same way. After going through the original carb twice, then finding a correct used one and going through it I have finally decided that it is evaporation and not much can be done about it. I have probably done at least a hundred Q-jets over the years and like Joe I dont think I have ever seen one with leaking bowl plugs.
My S-10 is pretty much the same way and it is carbureted too.
I've found pouring 3 ounces of gas into the ventilation tube fills the fuel bowl nicely. Then just one pump of the pedal and it starts most times. This avoids the long cranking process and the starter.
My Wifes Riviera is exactly the same way. After going through the original carb twice, then finding a correct used one and going through it I have finally decided that it is evaporation and not much can be done about it. I have probably done at least a hundred Q-jets over the years and like Joe I dont think I have ever seen one with leaking bowl plugs.
My S-10 is pretty much the same way and it is carbureted too.
It's interesting to me how many people throw this leaking well plug thing out there as a solution to these problems as if it's a slam dunk.
When these cars were new, they were driven more or less daily - to work, grocery store, church, what-have-you. A side effect of regular use was that there wasn’t as much time for evaporation, drain-back, leaky well plugs or whatever, the regular use of the car would keep the effect from surfacing.
Now these cars get irregular use. Sometimes I have days or weeks between using mine. Gasoline is a VOC. It will evaporate over time. I accept that and go out of my way to keep my batteries on trickle chargers when the cars are stored, I stay on top of my starter motors and try to keep “fresh” gas in the cars. If I know I’m not going to be using the car for a while, I don’t top it up. I leave maybe a 1/4 tank and when I get it out of storage, then I put “fresh” gas in with the weeks-to-months old fuel.
When they’ve been sitting for days/weeks, I picture the cam spinning and with each revolution, I picture the eccentric pumping the fuel pump arm up & down. After a bunch of revaluations, I stab the gas pedal in the tried and true way once I can picture the carb fuel bowl full. The engines rarely fail to start as designed.
FYI - the modern version of this problem is the computerized cars have to run at least every few weeks. All the computers on standby require battery power to hold their stored values. If the batteries run down, the computers reset to their default values and the cars don’t run so well until they’ve run a bunch of miles.
Action set for all of this is use the cars regularly and they’ll work their best.
When these cars were new, they were driven more or less daily - to work, grocery store, church, what-have-you. A side effect of regular use was that there wasn’t as much time for evaporation, drain-back, leaky well plugs or whatever, the regular use of the car would keep the effect from surfacing.
I don't think that is the issue. I think it is the ethanol in the fuel evaporating faster and I think most of it happens right after you shut the engine off and it is still hot. My Wife's Riviera was driven daily until she retired a couple of years ago and it is still driven at least a few times a week but if it sits more than a couple of days she has to go through the cycle once or twice. Same with my S-10 If I drive it to the shop every day it starts right up but if it sits all weekend it takes a couple of crank cycles to get it started.
Todays gas is formulated for todays cars. Modern cars have closed fuel systems, with electric fuel pumps. Fuel evaporation isn’t a concern.
Old iron with carburetors make up a very tiny percentage of fuel buyers. It doesn’t make sense for refineries to add the ingredients to prevent fuel evaporation.
Y'all know a few to 10 seconds of cranking isn't a bad thing. It gives the oil pump a chance to circulate oil throughout before the engine fires.
I actually prefer to crank mine until I see oil pressure then I set the choke,
Start up is where most wear occurs.
Evaporation is more prominent with today's **** gas. Ethanol evaps quicker. Try ethanol free gas. The choke system needs to be dialed in as well.
If you haven't driven the car in a couple weeks, you are outside its operating parameters and should realize that it will start, but will not be optimal. The cars were designed for daily driving. I expected a fully evaporated and gone fuel bowl at that timing.
Contrariwise, I expect a cold car that I drove yesterday to, with one depressing of the throttle to set choke and prime, then hold at 25%, to start within a couple seconds.
The critical point is, are you losing the gas via leakage out the bottom before it evaporates out? One can remove the carb, sit it over a tub, gravity load the fuel bowl via another fill line into the inlet, and see if it drips any over the next couple days.
March 31st, 2024, 07:04 AM
