Blue 253 warm starting issues

**Vombil** · 03-04-2017, 03:38 PM

Hi guys - bit of a novel but this is doing my head!
I have an 81 with original blue 253 and rochester. Original 260,000kms. Motor is breathing and there was some smoke out the tail pipe when i had 20/50 oil in it but have some additive in it now and it's not noticeable.

So, the car starts perfectly when cold (not like a normal Rochester though. absolutely no throttle is required) but when it's warm and you leave it for a few minutes it's very hard to start. The only way to get it to fire up is to hold the accel all the way to the floor and keep cranking. It will re-start perfectly if you turn key off and then straight back on again.

I thought maybe compression in valves/rings is an issue but it's not misfiring and plugs while look to be dirty and really black, are not all oiled up or white like when running lean if a valve is burnt/head gasket etc.
The rochester has been rebuilt at some stage but has fuel stains all over the outside and when you hit the accel pump it really gushes loads of fuel. I had considered it's getting too much fuel ???or heat soak where the fuel is boiling but the carby is not hot to touch when it's having problems starting. Solid metal fuel line from pump to carby. Could it have wrong pump? Wrong jets in carby, just needs tuning? I have not done a compression test. I once had a burnt valve on a blue 202 but you could see it ran rough and sure enough compression was down on 1 cylinder when tested.

Has correct spark plugs although they are quite old. I have gapped them at 1.5mm as per NGK recommendations. They were around 0.8-1mm. Vacuum advance working well. 12 degrees seemed to be good when plug gap was 1mm but 10 degrees idles better at 1.5mm plug gap.
I dont want to spend $500 on a carby re-kit and it does not solve the problem!

Would love to get some ideas from anyone with experience in these blue V8 engines. thanks in advance

**matt.p** · 03-04-2017, 03:49 PM

I will have a stab in the dark and suggest a possible vaccuum leak or manifold leak.

**Innuendo** · 03-04-2017, 04:36 PM

That could be it. Whilst running/idling spray some Areostart or Start You Bastard along the manifold edge and around all screwing fitting, carby base etc.
Don't allow any to go via the Air filter/Top of Carby. If the revs pick up from idle then you have found a leak.

My instant thought though was flooding. Holding the pedal flat the restart is an indication of a flooded engine.

**wbute** · 03-04-2017, 06:24 PM

Check the strainer in the carb where the fuel line screws in.
But if it starts with no throttle from cold I reckon there is a carb problem. Generally one pump per cylinder plus one for good luck. Are you sure it was oil smoke and not excess fuel going out the exhaust? The auto choke could be set wrong too. I didn't think quadrajets had jets as such. Metering rods.
It could be a hundred things. Vacuum leaks etc.

**Taily** · 03-04-2017, 06:54 PM

When it does start and idle when it is hot does it smell/look like it is fuelling-up?

All quadies have a couple of plugs under the main jets that are prone to dribbling fuel. I'm tipping if not a vac leak as previously mentioned it will be a pretty sure thing that one or both of these bad boys are leaking and piddling fuel straight into the throttle plate. Google is your friend to fix them, there is plenty of good info on the net about how to seal them up and get it running right. They look like a big complicated carby and they can be a little tricky to tune exactly right over about 300hp but they can be conquered.

A carby kit, a can of carby clean, a few basic screwdrivers and tools and a couple of spare hours one afternoon and you can have it running sweet again.

**Vombil** · 03-04-2017, 09:08 PM

Originally Posted by Innuendo

That could be it. Whilst running/idling spray some Areostart or Start You Bastard along the manifold edge and around all screwing fitting, carby base etc.
Don't allow any to go via the Air filter/Top of Carby. If the revs pick up from idle then you have found a leak.

My instant thought though was flooding. Holding the pedal flat the restart is an indication of a flooded engine.

thanks mate. I tried that already but with WD40 which i know isn't super flammable but yeah, no rev increase

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Originally Posted by wbute

Check the strainer in the carb where the fuel line screws in.
But if it starts with no throttle from cold I reckon there is a carb problem. Generally one pump per cylinder plus one for good luck. Are you sure it was oil smoke and not excess fuel going out the exhaust? The auto choke could be set wrong too. I didn't think quadrajets had jets as such. Metering rods.
It could be a hundred things. Vacuum leaks etc.

I just fired it up a few mins ago after it was running for only 30 seconds and it was a total bitch to get going again. when I did get it running it wasnt blowing anything (white or blue but light was poor) but it ran really rough until it must of pushed all the excess fuel through?? it's weird the carbie bloke is actually really poor with diagnosis. he just wants to rebuild everything. seriously, it's a full rebuild or fu$5 off apparently

**Valencia** · 03-04-2017, 09:14 PM

Get a second opinion on that carby

**Vombil** · 03-04-2017, 09:24 PM

Originally Posted by Taily

When it does start and idle when it is hot does it smell/look like it is fuelling-up?

All quadies have a couple of plugs under the main jets that are prone to dribbling fuel. I'm tipping if not a vac leak as previously mentioned it will be a pretty sure thing that one or both of these bad boys are leaking and piddling fuel straight into the throttle plate. Google is your friend to fix them, there is plenty of good info on the net about how to seal them up and get it running right. They look like a big complicated carby and they can be a little tricky to tune exactly right over about 300hp but they can be conquered.

A carby kit, a can of carby clean, a few basic screwdrivers and tools and a couple of spare hours one afternoon and you can have it running sweet again.

I could smell fuel with bonnet down about 10 mins after switching it off and it had only run for 30 seconds this arvo. When plug gap was 1mm it ran pretty OK after it fired when hot. Now with gaps at 1.5 it is rough for a fair few seconds longer and then runs fine. It so suss that it fires immediately with no hesitation and no pumps when it's stone cold, try restart it more than 20 seconds later, dreamin.

heard about the wells than need to be filled with epoxy. another bloke suggested needle and seat issue and another a float problem. I really want to rebuild one but i've seen one apart and it freaks me out! what a mess. The same carby bloke I use pulled one down years ago and showed me the base was warped and then asked me if i wanted to spend $750 for him to rekit it... when I said,, ah no -he boxed it up in 100 bits and sent me home

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Originally Posted by Valencia

Get a second opinion on that carby

got anyone close mate? I have a mechanic that will rekit and clean it etc for $70 plus cost of kit. If it needs parts, he has none. He's pretty old school so i trust he's got some idea.