So I got a used Dodge van a while back -- manual transmission, VIN "H" with 6 cylinders (if I'm reading the VIN properly; it's definitely 6-cylinder) -- and now it's having some problems:

-Trouble starting; starter is strong, and it will try to start, but usually nothing happens unless I push gas pedal hard (to the floor); if I do that, it eventually revs up high and immediately drops to a lower RPM; if I release the pedal immediately, it'll run weakly (otherwise it stalls) and usually dies eventually, but after 2-4 times it will keep running. UPDATE: This has stopped happening since I put new fuel into the vehicle.

-Before the motor begins to warm up, pushing the gas pedal will cause the engine to cough, or even stall out completely -- it tries to rev higher, but sounds like it's not getting enough fuel. If I tap the gas pedal in the right way I can slowly coax the engine to a higher RPM, but it sounds terrible.

-Once it begins to warm up, it will often jump to a very high RPM (3 krpm, maybe 4; there's no tach) and stay there; I haven't found a way to make it go back down immediately, but once it's run that way a couple minutes tapping the pedal hard will make it drop down again.

-Motor is weak and fires poorly under load

-Motor will start sounding throaty and coughing in higher gears when going up hills

-Being low on fuel (or having old fuel) seems to make all problems MUCH worse

Things I do know:

-All cylinders are firing consistently
-Compression is around 118-120 on all cylinders
-Fuel filter is brand new
-Mechanical connection between pedal and carb is sound; pedal return spring is fine.
-Starter is strong
-Alternator puts out plenty of power

Things I do not know:

-Maintenance history; I have no idea what was done with it before I got it, aside from a claim the clutch was new.
-Mileage: the odo rolls over at 100k, and it currently reads 21k, most of which was put there by the previous owner in the past couple years.

So given this info, I'd like some suggestions of what I should check, and how to check it; I'm sure it could be a bad fuel pump, but I don't know how to check if it's good or not, or what else the problem could be.

 

Battery first! you can get a check and make sure the Alternator is working properly. then Spark plugs and leads Radiator Cap. then fuel filter maybe pump as well. How many miles on it? there is plently of info on this page so read through it and keep updating.

But I am sure your first problem is the Battery.

 

gazza101: Thanks for the reply; do note that the plugs are all firing correctly (I tested them individually), and the fuel filter is brand new.

I also updated the original post to mention that the alternator is strong, and that new fuel has improved the initial fire-up of the engine (but none of the other problems have changed at all).

I did originally suspect the battery as the culprit for the poor start-up, but even when I connected a different battery (self contained jump-start unit) to ensure there was sufficient power to start, there were no changes; the new fuel, however, seems to have made a lot of difference.

However, the other problems are exactly the same. When the engine gets throaty, I know that the cylinders ARE firing, but they're making a sickly "pfft" sound instead of a proper "pop" -- which I'm certain means there's not enough fuel in the mix for whatever reason -- and as I mentioned before, I did check all the plugs individually to ensure they were clean and firing consistently.

 

Clogged catalytic covert?

 

Clogged CAT is one of the things that pop into my head while reading the posting. Also if it's fuel related, the idle control on the TB could be an issue.

One last thing to consider is the emission canister and hoses. If clogged, then the fuel delivery system gets out of whack.

 

So the Battery, it only has a limited amount of current it can supply, especially as they get older. I am guessing that it would need to be at least a 660 CCA rating. What happens with the battery is because the vans use such big batteries they are able to recover to a standard voltage and have enough storage in which to turn the starter motor get the engine running then rely on the alternator to generate the rest of the power for the battery. But what you will find is that the alternator can not give enough power to the system, (which it should not be doing it is there to charge the battery not give power to the battery, the lower the current from the alternator the better it means the battery is fully charged and does not need to use the alternator) also there is not a deep enough storage in the battery for the engine to run properly, which is why when you put a load onto the motor the lets say 10 Amps needed to idle all of sudden becomes 20 Amps to Accelerate you will find that your battery voltage will drop from 13.2 V to say 11.5 V before the Alternator picks up and boosts your supply back to 13.2 V @ 20 Amps which is what is causing your rough running.

Also a decent Oil filter and High Mileage Oil will help.

From what you Say I would be looking at spending about $500 to get this vehicle up and running however when you mention the high RPM it makes me think that there could be bigger internal problems and do you want to spend that money to find out that a lot more work needs to be done.

You must also remember that these motors are heavier duty and require a little more TLC than what your standard car would need.

 

gazza101,

If that's the case, then wouldn't the rough running even out once the alternator kicked in?

In other words, if it was just a moment of roughness every time I pushed the engine harder, that would make perfect sense -- but this is very even and consistent: if the engine load goes above some point X (if I push the gas pedal down too far when the vehicle is in gear), it simply gets rough and stays that way without any variation.

In essence, if I hit the gas too hard with the transmission engaged, the engine goes weak and pushing the gas down any further has no effect I can discern -- even though the engine has no problems revving up to 5krpm if it's in neutral.

So unless it actually takes more power to fire the cylinders when the engine is under load, the idea that it's a lack of power doesn't make sense -- because otherwise the increased power drain is simply from having to supply more fuel and fire the plugs more frequently (if I understand correctly) -- and if that was the case, I'd expect simply revving the engine at all to do this, even if it wasn't in gear.

Note that the weirdness of pressing the gas when the engine is cold, is VERY DIFFERENT from the behaviour when the engine is hot and under load; in one case, the engine tries to rev up, but starts coughing and stalls out in neutral; in the other case, the engine sounds throaty and gets weak under load, but seems 100% normal in neutral.

 

I've driven around without a working alternator with battery voltage at 11.5 or even less, and suddenly had it working again. The difference was noticeable, but not drastic.

You say new gas has helped somewhat. This means the old gas was very old correct?

This IMO, is your issue. Your old stale gasoline while sitting in the tank had a lot of condensated water mixed in. The gas in the carb varnished things up.

You put new gasohol in the tank, and the ethanol combines with the water and allows it to be burnt, but there is still too much water in the mix.

I'd also suspect the EGR valve sticking fully open
or the heat riser valve on the e manifold stuck open,

and a weak coil.

 

New gas helped with the starting, but nothing else -- and that particular problem only started recently.

I originally thought there might be water in the gas when this problem started happening in the Summer, so I ran some seafoam through it; at the time, I was also driving the vehicle extensively and it was getting refuelled regularly.

The problems starting are more recent, and I'd chalked them up to the weather, but they probably were stale gas, since it was parked for so long. However, there's no way the fuel is the primary cause of the running issues, because it was getting lots of fresh gas for a couple of months and exhibiting the same behaviour.

 

Just my $.02 worth. That Seafoam does a really good job of breaking up all the crud in your gas tank, and clogging the fuel pump filter.