V8 Won't Start

martynwhiteley

martynwhiteley

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V8 Won\'t Start

Couldn't get it to fire up yesterday.

It was cold and damp, and I tried all the techniques I was advised last time, like pumping the lever 10 or more times, but no joy at all.

The plugs were replaced at a service only about 6 hours use ago, but it looks like you need a degree in acrobatics to be able to get at them.

I suspect the first test would be to take off a plug lead, attach to a spare plug, and look for a spark. (btw it's a carb model Merc 5.7 V8, 1995).

I tried spaying WD40 over the coil and lead area.

But does anyone have any tips for starting a merc V8 in damp and cold conditions?

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Re: V8 Won\'t Start

You could try any of the proprietory engine starters - but I used to use a spray called GT85 from Halfords. Starts anything!!

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Re: V8 Won\'t Start

Thanks Dave.

I did have a half hearted go at spraying 'Easy Start' around the outside of the air intake cover, but to no effect. I tried easy start last time, and took off the plastic cover to ensure it went into the carb, but no joy.

Easy start worked well with the old perkins diesels in the P25 I once had, but I've had no success with petrols. Perhaps that indicates the prob is def ignition/electronic related rather than fuel - as you'd expect in cold and damp conditions.

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Re: V8 Won\'t Start

I've not used any of the ez start sprays for years. They raise the compression skyhigh on firing up. Knacker rings if used too often and are generally bad news for a petrol lump.
Way to look at it is logically. If it was running and you've done nothing to it then theres something amiss. Start at fuel and end up at ignition. WD40 is ok for dispersing water but repeated applications over time will build up a "dry skin" of the stuff that does the leccy's insulation qualities no good. Needs cleaning off every so often. I used to spray the power head of an outboard I had years ago. Needed de greasing once a year when the current tracked to earth. Better to use a pure silicon spray as it doesn't "dry" and repells water/damp for ages

So you've checked fuel and spark. Is it sparking when it should?. Is it a strong spark? Is the kill switch playing up? Loads to check just do it in a logical order.

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Re: V8 Won\'t Start

Be careful in checking for a spark that you don't create a big bang, if you pick a working cylinder you can easily fill the bilge with fuel vapour through the unoccupied plug hole....

If you have no firing at all then the problem is probably in the LT circuit (so check for 12v and gnd at the coil, and correct resistance through the LT windings), or the HT from the coil to the rotor arm (inc the dist cap).

Common problem with cold engines is the battery not being able to hold the voltage up under cranking so no sparks - giveaway for this is the engine will try to fire as you stop cranking (as the volts come up after disengaging the starter but before the engine rotation stops).

Try a booster battery, if she starts then start looking for low volts either at the normal battery (booster disconnected), or a volt drop on its way to the starter - try measuring the volts at the coil while cranking.

Hope this helps...

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Re: V8 Won\'t Start

HT electrics would be a good place to start looking - check for spark as described. If you have got one spark, test for others, could be dodgy plug leads etc. DONT GET THEM MIXED UP!

Damp inside distributor cap may be the prime suspect, but try turning her over in the dark first, you can sometimes see the sparks tracking.

Flooding (excess petrol) could be a secondary factor. Probably worth removing as many plugs as you can (easily) and turning her over to try and clear the fuel (though after an hour or so this will have cured itself).

If no spark, check LT side, especially kill switch if fitted.

Mate of mine never removed the plugs from his without having a packet of spares. Clumsy bugger always snapped a few due to awkward access.

Starting tip.

Big batteries, well charged. Apply minimum amount of 'start technique' to get the job done without flooding.

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Re: V8 Won\'t Start

I had a friend who had a similar problem. When asked, Seastart told him that the problem was "shit in the carburettor" problem was they didn't say how often!! /forums/images/icons/crazy.gif

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Re: V8 Won\'t Start

Thanks Simon,

I think you may have just hit the nail on the head with the one about low voltage.

The engine spins over well enough, and volt meter was reading close on 12 when statis, so I didn't think it could be a battery prob.

But I was surprised when I heard the radio volume disappear when cranking, 'cos I hadn't noticed it doing that before, and most crucially, although there was no attempt at all to fire whilst cranking, I did detect a very slight urge to perhaps fire when I did turn off the starter. I was curious about that, but it was so slight I put it down to a mechanical knock from the starter gear.

It was three weeks since I'd last used it, and MedDreamer was there at that time, and he usually leaves bad luck, so I suppose he could have jinxed the batteries that had seemed fine to date. However I did notice that the autobilge pump bypasses the battery isolators, and there was more than a normal amount of rain water collecting in the bilge, so I suspect the pump may have been operating a bit over the last three weeks.

Better charge the batteries and try again. My car experience of petrols has usually been that if there was enough power to crank, then there was enough to generate the HT, but I guess 8 plugs take a bit more juice than 4, and your logic seems to fit.



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Re: V8 Won\'t Start

Based on Chev engine which is notoriously difficult to flood, so I would look at electrics. Earlier Volvos used points type ignition, so following on from other good advice here, check points (if fitted) haven't closed up or been bridged by water. Quite often water will run off the back of the engine cover and get onto the electrics causing condensation to build up. Can't remember if this set up has ballast resistor or not, but check all LT conectors.

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Re: V8 Won\'t Start

It is a relatively common occurrence on V8's with a rochester Q-Jet carb. The inlet to the carb has a very small filter that blocks easily. Usually manifests itself as dying under power, but will still idle OK, unless it's totally blocked.
Best bet is to remove the filter completely and fit a bigger inline filter instead.

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Re: V8 Won\'t Start

If it's a Gen IV engine (ie 1990 ish) these have thunderbolt IV ignition.
Which is electronic ignition to everyone else. Only the very early mercruiser engines had points.

I would suggest a spark plug tester from halfords, just stick it on the dizzy cap end rather than the plug end and crank it over looking for the spark.

If you have lots of spark, pull off the flame trap (air filter assy) and pour a couple of capfuls of petrol down, crank it over and see if it fires.

You have checked the kill cord is connected properly? Common thing to overlook, it accidentally gets knocked out.

Never ever ever ever use easy start or any other starting additive.

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Re: V8 Won\'t Start

Yep !! Didn't read it as Merc did I. Thunderbolts suffer from corrosion on the plug connection to the ign module. Worth a check.

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Re: V8 Won\'t Start

Martyn - You might try looking at the ignition module which is a small attachment on the side of the distributor. Pull off the plastic cover and release the plug. Inside you will find 6 contacts. Spray with electronic cleaner and allow to dry. Reassemble and try starting. Worked for me.

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Re: V8 Won\'t Start

Remove air cleaner top, pump throttles a couple of time to prime, have assistant turn key to start whist holding choke flap closed (right hand side of carb as you look at it) small linkage that operates venturi flap, worked for me before now!

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Re: V8 Won\'t Start

somebody had to say it/forums/images/icons/smile.gif

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