The V8 Engine Saga continues

Fire99

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Hi people,

I need your help (again). You'll have to bare with me as i'm still pretty new to these old Volvo Penta V8 petrol engines.

Anyway, today i replaced the coil and the mechanical fuel pump with a second hand one from 'coastal'. Anyway i changed the coil first and she started ok and ran ok but i wasnt convinced by the pickup and coastal had mentioned the symptoms could be the fuel pump giving up.

Anyway i changed the pump and she started on the button and ran for about 30 seconds then stalled and would not fire.
On investigation it seems fuel is now no longer being pumped into the carb.

Obviously the mechanical fuel pumps are about as complicated as a lump of iron and i find it amazing that the pump has failed.

Anyway before i go getting the 'ump and putting the original back on is there anything else i should check in the fuel system?

I stripped and reassembled the fuel filter/water trap when changing the pump... do such things as air locks occur on such a simple setup? Plus would that occur if it happily pumped enough fuel in to run for a 30 secs before it gave up?

I know the filter/water trap has a bleed screw in the top but that had no effect..

Anyway a bit of urgent tech help would be appreciated as i'd like to get to the bottom of this one tomorrow?

Also a second question. Since the engine is effectively a Chevy 305 Small Block V8, is there any issue with buying an aftermarket fuel pump from the automotive field? Since A second hand VP one was dearer than a new chrome high flow one from an American V8 company...

Anyway thanks guys for all your help on this..

Nik
 

sonarbell

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I know its sounds daft, but have you checked for "full throw" of the Fuel Pump actuating lever. The other problem could be a vacuum created in the tank by insufficient "Fuel Tank Breathing". Check the Breather hose for kinks or collapsed internals. You could eliminate the whole tank and fuel pipe system by sticking a piece of hose into a gallon can and connecting direct to the fuel pump. Then running of that for a few minutes. Just some food for thought....
 

oldgit

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"aftermarket fuel pump from the automotive field"

Having spoken to a couple marine dealers in the distant past,do know that the cams/timing and few other bits are different on marine stuff,but would have thought that fuel pumps to be the same.Quite a few places doing american big block car parts around,so sourcing a pump should not be to difficult or financially scary.
Presume it is mechcanical pump and have you dismantled the pump to check the insides are clear of muck and rubber bits are not split etc.
 

Micky

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Had problems with a mechanical fuel pump once.
I done away with it and fitted an electric SU pump. Results were perfect.
 

Fire99

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Thanks guys for your posts..
Looking at the Solid State fuel pumps the biggest one (without going for the biggest cylindrical one) flows 34 US gallons (28 Imperial gallons) an hour but is only rated up to 180 bhp. My 200hp engine consumes far less than 28 gallons an hour. Would that be suitable or do i need to go by the hp rating (and pay twice the price.) ?
 

andy01842

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I did notice that the dry prime is only 0.3 meters i.e. the pump can only be 0.3 meters above the fuel or it wont suck the fuel up. could this be your problem. just a thought.
 

spannerman

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DO NOT use an automotive pump, the reason is that the marine version has a tube running up to the carb from the underside of the diagphragm, this so that if it leaks internally the fuel goes up to the carb instead of into the bilges, the car version doesn't have this as it just leaks out onto the road.
If it ran for 30 secs this would be on the fuel in the pump and float bowl, sounds like you have an airleak in the sysytem so go through it from the tank fitting to the pump inlet.
 

Fire99

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cheers for that.
I did a little research and found that to be the case regarding the extra outlet to the carb.
What is pretty annoying is that i can buy a very smart chrome high output automotive pump NEW for less than i'm charged for a second hand manky marine version..
A new Marine pump is over 3 times the price of an automotive one..

I'm sure the word 'marine' and 'rip-off' should be linked in the dictionary.
 

JKay

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I had the same symptons and that was the problem

a tiny cut in the pipe from the fuel pump to carb at the

connection

It pumps air in preference fuel

cheers Joe
 

Sneds

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"I'm sure the word 'marine' and 'rip-off' should be linked in the dictionary. "

Here here, do you have a local "back street garage" employing a mechanic rather than a "technician"?
Worked for me, good luck
 

Fire99

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Well i substituted the original pump back on and abra-cadabra the same problem. No fuel being sucked from the tank.
Pretty annoying since its not exactly the most complicated setup in the world.. (must be the sun getting to me! )

Anyway the only items that have been 'disturbed' are the water separator filter cannister being removed, the fuel pump and the flexible connection from the filter to the pump removed so my guess is:

a) Now both pumps are up the swanny (i did dismantle the original pump to give it a clean and to check the rubber diaphram.. perhaps a mistake.)
b) the water separator filter is not sealing... pretty unlikely methinks..
c) the connection from the flexible fuel line to the pump is sucking in air. (it has a step-down adaptor on it)

So my next trick in 'operation give Nik the ump' will be to buy a new flexible line with new compression fittings.. This is where my knowledge is crap.. Does anyone know off the cuff what size fittings go into a VP V8 petrol mechanical (carter) fuel pump? Or what line i need. I was gonna give ASAP a call..

Oh and if anyone could tell me what is needed to replace a mechanical fuel pump with an electric one that would be groovy too...
My question on that being how does the engine regulate fuel flow from the electric pump?

thanks again,

Nik
 

Its_Only_Money

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My suggestion would be to put a clear section of fuel pipe nearest the carb, that way you can see any air bubbles as they come through. I had a similar problem with a failed seal on a fuel cock - as it was the highest point on the fuel system it didn't leak fuel out, just air in! Easy to find with the clear hose in and confidence-inspiring to know its fixed.

An electric fuel pump should regulate itself (as does the mechanical pump).
 

Fire99

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Thanks Simon,

On the fuel pump issue.. Thats not strictly true, since the mechanical pump increases flow as the revs rise (since it is run directly off the engine) where-as an Electric one wouldnt..?
 

dpb

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The regulation is done by the float in the float chamber whatever the pump. I had a facet pump vitted to my V8 with no problems experienced. However, as the pump was live when the ignition was switched on I had a concern about the scenario of engine fire, hose damaged, engine stopped, fuel still being sprayed, ignition on. This was to some extent adressed by having a gas monitor wired so it would cut the pump,but even this has issues to consider
 

Fire99

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Thanks alot for explaining that.
Strewth i'm learning all about fuel systems at the moment. Just a pain im learning with my spanners while the Sun is out.. (understatement of the year)

I see you're point regarding the fuel issue. Theoretically could i mount the pump near the tank so it was the other side of a bulkhead from the engine? This would mean it would be pushing past the water separator..

regards,

Nick
 

ValleyForge

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Yonks ago I had a 1966 4.2 Sunbeam Tiger (bought for £450 !). This had 2 SU fuel pumps in tandem - Flat out both went like the clappers & still couldn't give enough juice ....
 

Fire99

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oh yes...doh!! (too much cursing at the weekend!)

So any ideas if a solid state pump flowing 34US gallons would be up to the Job? it states 180bhp and my motor is 200hp but mine certainly doesn use 34US gph
 

Micky

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You can get all types of high pressure electric fuel pumps. Drag cars use use them and they can deliver more then enough fuel to run far more powerful engines then a boat engine.
If fitting one, connect it to a separate on/off switch, not directly to your ignition switch. You could also fit an automatic fuel cut off switch. Have a word with the drag racing boys.
 
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