Got spark and fuel, won't fire

Tofufi

Tofufi

Member
Hi all,

In the last week, I've been having issues with my P6B.

It's a 3500 with a Holley 390 carb, edelbrock manifold and Mallory dual point distributor.

Parked it up after a run of about 10 miles, upon which it was running fine.

Went to start it a couple of days later (following some heavy rain) and it won't start. A week later, it still won't go. It won't even cough or backfire.

Things I've checked so far:
The king lead gives a good strong spark from it to the engine casing.
Using a spare plug shows the plugs are getting sparks, although I'm not sure how strong they are.

Fuel is getting to the carb and is squirted down the inlet neck as I'd expect, and cranking it for long enough gives a fuel smell to the exhaust.

I've not altered the ignition timing, so I'd be surprised if this had suddenly jumped...

Any thoughts before I pull my hair out? It's not previously had this sort of trouble ever in the 3 years I've owned it...

Thanks in advance :)
 
Thanks for the suggestion :)

I've tried a new rotor arm and a new distributor cap. Neither of these seemed to have any effect... :(
 
Whip the plugs out to check if they are wet, you may have a ignition fault or have inadvertently flooded the engine. If the plugs are wet, let them dry out, old school method is to put them in the tail pipe of a running car a few at the time. Instant drying and warming up. If you can isolate the fuel delivery to the carb, crank the engine over on the starter for say 15 secs.. then again. You may have 'bore wash' from excess fuel in the cylinders. this helps to restore combustion pressure. If your happy your getting KV down to the plugs (all of them) then put them back in and restore your fuel supply... See what you have
 
I suppose it's fairly easy to flood the engine with the Holley carb.
Have one of your sets of points closed up/ look excessively worn?
Did you check the sprung centre carbon button in both caps to see if they make good contact with the rotor arm?
If the spark isn't strong enough perhaps your coil is at fault
Jim
 
i've had the problem before where a flooded engine wouldnt evapourate the fuell in very cold weather... have the spark plugs out to give it somewhere to go maybe???

Rich
 
Thanks all for the suggestions.

Managed to get it to start eventually. I'm still unsure what did the trick.

Pulling a plug showed that fuel was getting through. While checking the timing hadn't changed, it started coughing and spluttering when on the starter. 5-10 minutes of running really roughly, including refusing to idle and it ran better again.

I found the flame traps breather pipes between the rocker covers and air filter contained water, which was spitting into the air filter - I'd imagine this could have been the cause of the running issue.

The question is what is the cause? I've been doing a lot of short journeys in it lately, in very cold weather - perhaps this could cause condensation in the top of the engine?

When the engine had warmed up, there was a fair plume of steam coming from the rocker cover vents. Emptying the flame traps didn't show any sign of the water in them being coolant coloured. I did about 20 miles, including a motorway stint in the third lane, and even after that there was still steam coming from the rocker covers...

I guess a compression test is on the cards. :)

Engine:

DSC_2289.jpg


Steam at idle after 20 mile run:

DSC_2413.jpg


Some of what was in the air filter - what was coming out after the 20 mile run was just watery, not very oily.

DSC_2414.jpg
 
Hi, have a look in the rocker covers is there any 'mayonaise' in there? Have a look at the
dipstick is the oil 'milky'? The short journeys can be problematic in that it causes water in
the atmosphere to condense on the inside surface of the rocker covers once it starts it only
ever gets worse. the trouble can be that the water doesn't stay in the top of the engine, it
ends up in the bottom of the sump. If the answers to the questions are just a.little then you
may get away with getting the engine up to temp on a long run to try to burn off the water.
If there is too much in there then an oil change is the answer.

Colin
 
colnerov said:
Hi, have a look in the rocker covers is there any 'mayonaise' in there? Have a look at the
dipstick is the oil 'milky'? The short journeys can be problematic in that it causes water in
the atmosphere to condense on the inside surface of the rocker covers once it starts it only
ever gets worse. the trouble can be that the water doesn't stay in the top of the engine, it
ends up in the bottom of the sump. If the answers to the questions are just a.little then you
may get away with getting the engine up to temp on a long run to try to burn off the water.
If there is too much in there then an oil change is the answer.

Colin
Click to expand...

Thanks Colin.

Rocker covers appear as clean as usual - no mayo visible. I suppose the moisture forming shouldn't surprise me - my other car does make some mayo over the same journey, and that can't be head gasket failure as it's aircooled. :LOL:

Plugs:

DSC_2415.jpg


DSC_2417.jpg


DSC_2418.jpg


I'll keep an eye on it and see how we go - also will try to take it on a few longer runs where possible - thanks :)
 
Hi, thinking some more about this problem, a couple of thoughts occur. On your short journey,
cold morning runs you may be getting carb icing which subsequently leaves water in the manifold
hence stopping it starting long enough to flood. The other thought was the longer lengths of
uninsulated breather pipe causing more surface area for condensation.

Colin
 
colnerov said:
Hi, thinking some more about this problem, a couple of thoughts occur. On your short journey,
cold morning runs you may be getting carb icing which subsequently leaves water in the manifold
hence stopping it starting long enough to flood. The other thought was the longer lengths of
uninsulated breather pipe causing more surface area for condensation.

Colin
Click to expand...

That's a fair point - I've only experienced carb icing with this setup when it's been below freezing before, but the lack of inlet temperature control does concern me a bit.

Will see what I can do to shorten the breather pipes and avoid condensation running into the engine :)

Thanks for the suggestions :)
 
Right, me again. :(

I've still got the same problem as above - I don't think I ever fixed it at all, it just temporarily resolved itself.

Now it will run sometimes, and splutter. Some times it will run quite well, and just occasionally stutter, giving a slight jerk to the car occupants. Other times, perhaps a mile down the road, it'll run like a pig, only running when pumping the throttle, and refusing to idle. No power and sounds like it's not running on all cylinders.
After churning it on the starter motor, it'll sometimes pick up and run quite well for a few minutes, before going back to being a pig again.

I've tried replacing ALL the fuel in the car, in case it was old/bad fuel, and no improvement.

I'm wondering if it's a dirt/blockage in the carb, but when I dismantled the front half of it it seemed extremely clean. There's no muck apparent in the fuel filter.

I couldn't find any jets inside it to clean/blow through.

When you pump the throttle, the throttle pumps in both the front (front of the car) barrels of the carb squirt fuel down the inlets...

Has anyone any experience of a Holley 390? I've a Holley 390, Edelbrock manifold, Mallory dual point distributor, and an electric fuel pump.

Thanks, Jim :)
 
I don't like Holleys on RV8's, and so consequently don't know much about them, but if you can keep it running by pumping the throttle when otherwise it would stall, then it has an accelerator pump (which is the reason you can do that, and what shoots the jets of petrol), and so I'd guess that the main jet(s) is(are) blocking up intermittantly. There must be jets in there somewhere.
 
That makes sense. It's just a shame I've not been able to find those jets. :LOL:

Thanks for the confirmation that I'm (hopefully) on the right track :)

The Holley 390 is a horrible design too, I believe you need to remove the float bowls to access whatever jets are fitted. And the float bowls are side mounted, meaning the only way to empty them is to pour fuel over your engine :LOL:

When I say it will keep running when pumping the throttle, it often sounds like it's not running on all cylinders. Sounds dog-rough, to be honest.

That said, I really don't get on with SUs either.

Give me Dellorto or Weber downdraughts any day :)
 
I've had a quick google, and it appears you set the float height through a sight glass, and the jets are inside somewhere, under a cover, but by the sounds of it, reasonably accessible. Because they're such a popular carb in the States there's loads of info out there for them. Get those fingers working on your keyboard, just remember that for every good bit of info out there, there's hundreds of bits of rubbish.... You just need to work out which is which.
 
Perhaps it's the petrol I swallowed earlier while trying to siphon some fresh fuel for the Rover from my van, but I've tried searching several times, including an hour or so today, and not found anything which I recognise. :oops:

I'll go and dismantle mine, and take some pics. :)
 
OK, apologies if I'm a little grumpy as this is really frustrating me at the moment. My van appears to need some work too, and I need one of them working to drive to work on Monday...

Here goes with the pictures...

Carb complete:

DSC_4102.jpg


Float removed:

DSC_4104.jpg


With the sighting screw removed, the fuel level was almost perfectly to the level of the bottom of the sight screw, suggesting there isn't a problem with the fuel level.

What I believe is a metering block, with two jets and a power valve:

DSC_4105.jpg


Metering block removed:

DSC_4106.jpg


The two jets - both stamped 512. Neither appeared blocked, but I've blown them through.

DSC_4108.jpg


The other bowl has no metering plate - I believe this is blocked off?

DSC_4109.jpg


In addition, the throttle plates on the back half of the carb do not move at all when the accelerator is operated.

Any thoughts on where to go from here?

Thanks again, the help is much appreciated :)
 
Tofufi said:
In addition, the throttle plates on the back half of the carb do not move at all when the accelerator is operated.
Click to expand...

They're vacuum operated, so won't if you're just checking at rest.
 
harveyp6 said:
Tofufi said:
In addition, the throttle plates on the back half of the carb do not move at all when the accelerator is operated.
Click to expand...

They're vacuum operated, so won't if you're just checking at rest.
Click to expand...

Ahh, that makes sense. Thanks!

Other than blowing through the two jets and (what I believe are) the idle control screws mounted on the side of the metering plate, have you any thoughts as to what else I should do before re-assembling? :)

Thanks,
Jim.
 
If they are idle jets, then I would think there should be main jets hiding somewhere, but I just don't know enough about them to even be certain of that, or to add much more than I've said already.

One of my pet hates is people, particularly on the 'net, going on about things which, if anyone reads it who actually does know what they talking about, it's blatently obvious to the latter that the initial poster hasn't got a clue what they're talking about. I have no wish to look like the former, so I'll leave it at that, and I'm certainly not overkeen to make the effort to become the latter, so that's me pretty much done... :LOL:
 
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