Poor Running 1995 110 3.5 V8

nolift911 · Aug 30, 2022

Good afternoon mates -

Trying to diagnose a poor running condition on a 1995 3.5 V8 dual carbs. Issue comes and goes so it hard to diagnose. Generally shows itself after a hot restart. Smells like it is running rich or the choke is stuck. Pulled plugs after and they are dry so not sure exactly if it is a running rich issue or other. Seems to give black smoke and smells like fuel out the back though when it happens. Let it sit for 15-20 minutes all good, sometimes never comes back after driving but has been acting up lately. When it happens when I am driving it seems like it has gone into limp mode, no power, won't idle etc.

Any thoughts? carbs are topped up, checked the ignition components and they checked out ok.

Thanks -

tottot · Aug 30, 2022

Check the coil, have a feel of the case when the running goes poor. If case is getting hot could be on the way out resulting in poor spark at times.

nolift911 · Aug 30, 2022

Interesting that you say that - was driving it today when it happened and I was thinking - feels electrical. Checked the resistance (not running) and it showed 1.0 so it seems in spec...it looks old to me though so was going to swap out to see, cheap thing to change. It's just difficult to diagnose when it happens, I can't keep it running and still mess around in the engine bay when it happens. It normally runs great and no issues without this issue - annoying.

nolift911 · Sep 2, 2022

Replaced the coil - no change. Went out on me this morning. Was on a hot restart...have to use choke to keep it running, so it feels like not getting enough fuel and black smoke coming out the back. Let it sit 15 minutes and works fine again. I think I am going to rule out an ignition issue...carbs?

tottot · Sep 3, 2022

If you are getting a nice fat spark even if when running rough [ use a spare plug on one lead to test ] unlikely ignition.
Having choke to keep running suggests lack of fuel. Running black with choke on suggests it is now drawing more than enough fuel due to the extra suction developed in the manifold.
What sort of fuel lift pump do you have ?

nolift911 · Sep 3, 2022

tottot said:
If you are getting a nice fat spark even if when running rough [ use a spare plug on one lead to test ] unlikely ignition.
Having choke to keep running suggests lack of fuel. Running black with choke on suggests it is now drawing more than enough fuel due to the extra suction developed in the manifold.
What sort of fuel lift pump do you have ?

Fuel lift pump? Its a bone stock 95...so not sure. It also came with dual tanks and dual pumps...you fill by lifting the passenger seat. Could it be some type of evap type blockage? I never use the spare tank, its basically empty. There is a switch under the dash that actives and can switch them. What about needle seats in the carbs...I am at about 149 kilos.

Turboman · Sep 3, 2022

nolift911 said:
Fuel lift pump? Its a bone stock 95...so not sure. It also came with dual tanks and dual pumps...you fill by lifting the passenger seat. Could it be some type of evap type blockage? I never use the spare tank, its basically empty. There is a switch under the dash that actives and can switch them. What about needle seats in the carbs...I am at about 149 kilos.

What sort of fuel are you using?

I should think that engine ran on leaded 4 star originally. Modern fuel isn't the same.
Maybe it has eaten rubber components in the fuel system, and that is causing jet blockage, or similar problems.

nolift911 · Sep 3, 2022

Turboman said:
What sort of fuel are you using?

I should think that engine ran on leaded 4 star originally. Modern fuel isn't the same.
Maybe it has eaten rubber components in the fuel system, and that is causing jet blockage, or similar problems.

Yeah possibly - we only have ethanol (10% max) around me. Needles and seats in the carbs? Just trying to figure why only when hot or after restart. The other day it was acting up and I needed to get him home - midway through the drive home it cleared on its own. I did try adding some fuel additive/stabilizer but did not do too much. I am reasonably handy around cars but SU carb rebuilding would be a stretch...

Turboman · Sep 3, 2022

nolift911 said:
Yeah possibly - we only have ethanol (10% max) around me. Needles and seats in the carbs? Just trying to figure why only when hot or after restart. The other day it was acting up and I needed to get him home - midway through the drive home it cleared on its own. I did try adding some fuel additive/stabilizer but did not do too much. I am reasonably handy around cars but SU carb rebuilding would be a stretch...

Doubt if metal parts have worn badly enough to make a noticeable difference to running at that mileage.
The carbs are easy to rebuild, you can get a kit of seals etc.
Take the carb apart, noting carefully where everything goes, and how far the adjuster screws were screwed in.
Then give the whole carb body a good rinse of with carb cleaner, blast it into all the holes and apertures, inside and out.
If you do this on a white sheet, you will get a good idea how much crud came out.
Then rebuild on the clean body, using all new seals and jets, which may also come in the kit.
Do not use sealant, a common cause of fuel system blockages.

kermit_rr · Sep 3, 2022

Have you checked the diaphragms in the to of the strommies? That would make it run crap and feel like it's not getting enough fuel

leo777 · May 31, 2023

I'm a bit late to the party but I had the same issue with my old 3.5 on SU carbs. The spark was fine, it was intermittently rough and when I striped the carbs, I found that the one of the floats in the base of the carb was not floating as it was full of fuel. Over fueling and flooding the engine. Best of luck

Poor Running 1995 110 3.5 V8

nolift911

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