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[GMCnet] Starting - does it have to take so long [message #358592]

Mon, 14 September 2020 05:12

Olly Schmidt

Messages: 1265
Registered: February 2014
Location: Germany and Scottsville, ...

Karma: 8

Senior Member

Hi group,

I like my GMCs, but one thing that I am not happy about, is the time it
takes to start the engine.

Should a perfectly setup Quadrajet carburetor be able to start each and
every time after 2-3 seconds max?
Or is this only achievable with a more modern replacement?

Any and all thoughts are highly appreciated.
--
Best regards

Olly Schmidt
PGP KeyID: 0x4196BF22
'76a 26' Eleganza II - Virginia, US (transmission broken)
'73 23' Sequoia - Schleswig-Holstein, Germany

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Best regards

Olly Schmidt
PGP Key ID: 0x18a9 3a1f 4196 bf22
'76a Eleganza II, VA
'73 Sequoia, SH, Germany

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Re: [GMCnet] Starting - does it have to take so long [message #358594 is a reply to message #358592]

Mon, 14 September 2020 06:23

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

Slow starting is usually one of two things.

The gas has boiled out of the carb on engines without the exhaust cross over blocked. You have to wait for the pump to fill the carb again.

Or the automatic choke is not adjusted correctly.

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

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Re: [GMCnet] Starting - does it have to take so long [message #358595 is a reply to message #358594]

Mon, 14 September 2020 06:34

Olly Schmidt

Messages: 1265
Registered: February 2014
Location: Germany and Scottsville, ...

Karma: 8

Senior Member

On 14.09.20 13:23, Ken Burton via Gmclist wrote:
> Slow starting is usually one of two things.
>
> The gas has boiled out of the carb on engines without the exhaust cross over blocked. You have to wait for the pump to fill the carb again.
>
> Or the automatic choke is not adjusted correctly.
>

So you are saying: Yes, a properly setup original setup should start
within a 2-3 second period max?

--
Best regards

Olly Schmidt
PGP KeyID: 0x4196BF22
'76a 26' Eleganza II - Virginia, US
'73 23' Sequoia - Schleswig-Holstein, Germany

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Best regards

Olly Schmidt
PGP Key ID: 0x18a9 3a1f 4196 bf22
'76a Eleganza II, VA
'73 Sequoia, SH, Germany

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Re: [GMCnet] Starting - does it have to take so long [message #358597 is a reply to message #358595]

Mon, 14 September 2020 07:20

kstockwell

Messages: 367
Registered: May 2016
Location: Putney VT

Karma: 4

Senior Member

I put a new starter in mine a few years ago and I was shocked at how quickly it started even when cold. the 2-3 seconds you talk about

Of course when the starter was really dying it didn't want to start when hot. It's a pretty cheap easy fix, I also ran new wires to the engine battery.

When the starter took so long to crank it meant I was flooding it- even with a newly rebuild and set carb it still took awhile to start up.

I now: turn the key to run, hold my foot on the gas for 5 seconds or so, then crank. When the starter and battery were brand new it instantly started, now it's 10 seconds of cranking or so if it's been sitting for a week or more. If it's been running it starts in 2-3 seconds

1978 Kingsley Putney VT

[Updated on: Mon, 14 September 2020 07:23]

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Re: [GMCnet] Starting - does it have to take so long [message #358599 is a reply to message #358592]

Mon, 14 September 2020 07:35

RF_Burns

Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada

Karma: 3

Senior Member

Olly,
I'm thinking the biggest reason for long cranking before starting is fuel boiled out (evaporated) from the fuel bowl in the carb, like Ken said. Even if the cross-over is blocked which helps a lot, the carb is sitting on top of a large engine which takes a while to cool. Also most motorhomes tend sit for a long time giving ample time for the fuel to evaporate.

When this happens, the fuel pump must pull fuel through about 20 some feet of fuel line and up to the carb before it even starts to refill it. Of course this only happens with the OEM fuel pump when you are cranking the engine...so you crank and crank and crank...

by adding an electric fuel pump with a momentary "Prime" switch, you can bypass the cranking and just push the Prime button for a few seconds to fill the carb. Now it should start within the 2-3 seconds you desire.

So to answer your question "should a properly setup original setup should start within a 2-3 second period max?" I'm guessing they never did due to the hot crossover and usual extended time between starts would leave it with an empty fuel bowl.

I have EFI and the fuel pump runs for several seconds as soon as I turn the key to IGN this primes the fuel system to ready for start. It always starts in about 1-2 seconds. I have a "Prime" button for my Onan generator as it has the same empty fuel bowl issue. I press and hold the Prime button for a few seconds (I can hear the fuel pump change tone when the fuel bowl is full), then I hit the start button and it starts within 2-3 seconds.

Interestingly my new GMC pickup truck with direct injection, runs the fuel pump for a few seconds as soon as I open the driver's door. This primes the fuel system in preparation to start.

Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

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Re: [GMCnet] Starting - does it have to take so long [message #358606 is a reply to message #358599]

Mon, 14 September 2020 08:02

Dolph Santorine

Messages: 1236
Registered: April 2011
Location: Wheeling, WV

Karma: -41

Senior Member

Bruce

I was getting such fast starts with the Howell EFI that I used a timer module to delay start for oil pressure to come up in the engine before putting spark to it.

It’s not much, but the 2-3 seconds of cranking is much more like a Q-Jet than a modern EFI system.

The oil pressure comes up, and then spark is put to it.

I don’t know if alleged science behind this makes sense, but it seems to.

Dolph

DE AD0LF

Wheeling, West Virginia

1977 26’ ex-PalmBeach
Howell EFI & EBL, Reaction Arms, Manny Transmission

“The Aluminum and Fiberglass Mistress”

|[ ]~~~[][ ][] \
"--OO--[]---O-"

> On Sep 14, 2020, at 8:35 AM, Bruce Hislop via Gmclist wrote:
>
> Olly,
> I'm thinking the biggest reason for long cranking before starting is fuel boiled out (evaporated) from the fuel bowl in the carb, like Ken said. Even
> if the cross-over is blocked which helps a lot, the carb is sitting on top of a large engine which takes a while to cool. Also most motorhomes tend
> sit for a long time giving ample time for the fuel to evaporate.
>
> When this happens, the fuel pump must pull fuel through about 20 some feet of fuel line and up to the carb before it even starts to refill it. Of
> course this only happens with the OEM fuel pump when you are cranking the engine...so you crank and crank and crank...
>
> by adding an electric fuel pump with a momentary "Prime" switch, you can bypass the cranking and just push the Prime button for a few seconds to fill
> the carb. Now it should start within the 2-3 seconds you desire.
>
> So to answer your question "should a properly setup original setup should start within a 2-3 second period max?" I'm guessing they never did due to
> the hot crossover and usual extended time between starts would leave it with an empty fuel bowl.
>
> I have EFI and the fuel pump runs for several seconds as soon as I turn the key to IGN this primes the fuel system to ready for start. It always
> starts in about 1-2 seconds. I have a "Prime" button for my Onan generator as it has the same empty fuel bowl issue. I press and hold the Prime
> button for a few seconds (I can hear the fuel pump change tone when the fuel bowl is full), then I hit the start button and it starts within 2-3
> seconds.
>
> Interestingly my new GMC pickup truck with direct injection, runs the fuel pump for a few seconds as soon as I open the driver's door. This primes the
> fuel system in preparation to start.
>
> --
> Bruce Hislop
> ON Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> My Staff says I never listen to them, or something like that
>
> _______________________________________________
> GMCnet mailing list
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Re: [GMCnet] Starting - does it have to take so long [message #358607 is a reply to message #358592]

Mon, 14 September 2020 08:58

JohnL455

Messages: 4447
Registered: October 2006
Location: Woodstock, IL

Karma: 12

Senior Member

Could be
1) weak accelerator pump
2) improper driver start procedure for a Qjet
3) leaky bowl plugs
4) improper choke operation or setting

So if coach has been sitting a week or so it takes about 5 seconds cranking to get fuel bowl full.
Otherwise, starts should be instant. In fact faster than modern EFI using crank and cam sensors. The cam sensor needs to get a good pulse to the computer to find 1 and that alone can take 2 full crank revolutions.
Read the cold and hot start procedures in the owners manual. Many do it wrong.

Dolph my take is you should be delaying fuel not spark if you want delay. Otherwise you are cranking and spraying in fuel and washing lube off walls. Remember at cranking speed the crank throws are not slinging oil up on the walls, especially when cold,

John Lebetski
Woodstock, IL
77 Eleganza II

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Re: [GMCnet] Starting - does it have to take so long [message #358610 is a reply to message #358592]

Mon, 14 September 2020 09:47

lqqkatjon

Messages: 2324
Registered: October 2010
Location: St. Cloud, MN

Karma: 5

Senior Member

to simply answer your question:

yes- should start right up.

now to drive away, they can, but that is a little more rare to have one tuned in that well with the choke and everything else. but not that hard to get it to fire right up, then let it warm up a minute or two, then drive away. Unless you are running efi.

Jon Roche 75 palm beach EBL EFI, manny headers, Micro Level, rebuilt most of coach now. St. Cloud, MN http://lqqkatjon.blogspot.com/

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Re: [GMCnet] Starting - does it have to take so long [message #358613 is a reply to message #358610]

Mon, 14 September 2020 10:10

Olly Schmidt

Messages: 1265
Registered: February 2014
Location: Germany and Scottsville, ...

Karma: 8

Senior Member

On 14.09.20 16:47, Jon Roche via Gmclist wrote:
> yes- should start right up.

Thank you all for making it clear that it should start right up. Now I
have a goal :-)

--
Best regards

Olly Schmidt
PGP KeyID: 0x4196BF22
'76a 26' Eleganza II - Virginia, US (transmission weeps getting hot)
'73 23' Sequoia - Schleswig-Holstein, Germany

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Best regards

Olly Schmidt
PGP Key ID: 0x18a9 3a1f 4196 bf22
'76a Eleganza II, VA
'73 Sequoia, SH, Germany

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Re: [GMCnet] Starting - does it have to take so long [message #358615 is a reply to message #358592]

Mon, 14 September 2020 11:13

RF_Burns

Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada

Karma: 3

Senior Member

John,
The Howell/EBL system does not inject fuel until it sees ignition pulses. If Dolph is not applying power to the HEI, then there are no ignition pulses to the ECM and no fuel will be injected.

No fuel is injected when you shut the key OFF and the engine is winding down. Hence less wash-down of fuel during shut-down.

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