I use my 90 W 150 as my winter rig but the last 2 years it's been hard starting and bucks/shakes and stalls when cold.
It will pretty much start right away if you pour some gas down the throttle body to prime it. But if not it needs to crank for 30 secs or more to eventually fire. As you can imagine I've killed a couple of starters already. Once it's running it runs like crap. It kinda shakes at idle and will want to die when you put it in gear. Once moving the truck bogs and shakes pretty bad at anything under about 1/4 throttle. You have to feather the throttle or push pedal about 1/2 or more and it eventually clears itself up and takes off. Going down the road it's more or less OK, but the fun starts again when you have to stop.
It starts up and runs OK when warmed up, but not great and certainly not perfect like it used to.
Not knowing much about these systems I threw a bunch of parts at it hoping to fix it but it's still pretty much the same.
From what I can remember within the last year or so it has a new:
MAP sensor
Oxygen sensor
Throttle position sensor
Temp sender
EGR valve
Fuel pressure regulator
I also checked the wiring harness under the hood and found some corroded splices but fixing them didn't help either. I have another computer to try but other than that I don't know what else.
Sorry for the long read but can anyone give me ideas? Where is the ASD relay? Could it have something to do with it?
You should test the fuel pressure ASAP. It should be 14.5 +/- 1 psi. I'll bet its low causing the drivability problems and I'll bet it falls rapidly as soon as you turn it off, likely contributing to the starting problems.
It could be electrical, but start by testing fuel pressure.
Is there a port to check the pressure on or do I have to tee into the fuel line somewhere? I don't have a fuel pressure gauge that will read that high, will an old oil pressure gauge work?
its only 14.5 psi / just about all TBI problems are sensors or wiring at the back of the right valve cover connections / have you pulled the CODES / l,d start there
What those relays or plugs on the right valve cover for anyways? Do they go bad or is it usually a wiring problem? Anyone have a wiring diagram for one of these trucks?
I have checked the codes before but I'll check them again.
So if the fuel pressure checks low is the fuel pump bad for sure?
in the picture below right were it says to engine wiring / THOSE connectors are the ones that cause most of the TBI problems / do a search on here for it
Hey my 90 Rc done the exact same thing two weeks ago (you can probably find my old post with all the sugested fixes.) but after doing the same as you replacing parts and asking for help I found the Positive batt. wire connection bad.
I couldn't believe thats all mine was after all the time and money spent under the hood.
Good luck.
warm the truck up,,
shut it off.
discon the batt. this will clear the codes.
reattach the batt.
run the truck for a little while.
now check for codes by cycling the ket 3 times
report back with the codes.
the Hall Effect sensor will cause problems with out throwing codes.
I have the truck warming up now, I just drove it around for the first time in a week. It still has that shakey idle and stumbles BADLY when trying to accelerate, like a big lag between the time you push the gas pedal and when the truck moves. It doesn't have much of a problem driving down the road though once you get to a certain speed like I said.
As I understand it most of the codes I'm getting are normal for a 4x4 with no AC and no cruise, yes?
The only weird one is 45 (for a turbo fwd?). I had the battery out last weekend for a charge anyways so the codes should be "fresh" but I'll shut the truck off now in a few minutes and unhook the battery.
Yes I looked. Most times it seems the hall effect is the culprit? That's one thing I didn't change...
As for the codes nothing seems to jump out as being wrong.
12 - battery disconnected
33 - Normal for no AC
37 - Normal for 4x4 without lockup
34 - Speed control solenoid(s) circuit is open or shorted - Normal for a truck without cruise?
45 - This is the only weird one, only info I can find is for a Turbo car
55 - end
There is a idle position motor / Gear solenoid. Mine is noisy . Everytime you start or turn off engine it cycles. Do you hear / see anything under the hood when you turn on the ignition before you turn to start?
Id change the Hall Efect sensor. My 88 was running eratic after I did a engine transplant. The HE sensor was at fault. New 1 from O'Rilies was $26 bucks...
According to this pdf, code 45 also means open or short in the overdrive circuit, which makes sense because a previous owner of my truck replaced the 518 with a 727.
Also, I hear what I assume is the ASD relay clicking when the key is turned on, but it seems to click off again right away, or I am not hearing it click off. Should stay on for 2 seconds to prime it?
Also, I hear what I assume is the ASD relay clicking when the key is turned on, but it seems to click off again right away, or I am not hearing it click off. Should stay on for 2 seconds to prime it?
Thats correct, it should do that. I don't think its even 2 secs, but what ever, its when the computer gets the pulses from the hall effect, that the computer knows the engine is starting, and turns it back on.
So does anyone else think it could be the hall effect? It seems more like a fuel delivery problem than ignition, but I don't really know. I can't find my old gauge to check fuel pressure yet,but in the meantime i'll check those connections on the valve cover.
Just hold your hand on the ASD relay, and reach inside or have someone turn the key, you will feel the ASD relay kick on, then off, then turn the key to start, you should feel it click again. By all your description, I bet you won't.
The ASD relay is what gives power to the coil, and the fuel pump. Without the computer seeing the pulses from the Hall effect, it will not turn the ASD relay (and the coil, and the fuel pump) back on.
The hall effect, or the wiring, is about the only no start condition that will not show a code. Theoretically, it should show a code 11, But our computers were not programed to show that.
No need to worry about the fuel pressure, if you do not feel that third click on the ASD relay.
Just hold your hand on the ASD relay, and reach inside or have someone turn the key, you will feel the ASD relay kick on, then off, then turn the key to start, you should feel it click again. By all your description, I bet you won't.
I couldn't feel it click the first time I turned the key, but could feel it the second time and then it started. Problem is though, even when it's running it doesn't run right.
How about a old oxidized tank of fuel? How long has it been sitting, have you considered draining it and starting with fresh fuel?
Not sure about stores in Newfland but quite a few auto parts stores in the US will loan you a fuel pressure test rig with all needed connections. You will have to "t" into the supply line as there is no test port.
The issue with the Hall effect is there is no easy or cheap way to test these and they seem to fail a little bit at a time and our computer can't figure it out and throw a code. It's 20+ years old, replace it. I hate saying that as it's the throw parts at it till it runs method of fixing stuff which we hate here on RCC.
It had been sitting about 5 months, but it had very little gas in it. I put in about 10 gallons of fresh stuff on top of it before I started messing with it.
Fuel filter is about a year old, ditto for cap and rotor. Still has the same plugs and wires as when I bought it though, and I have no idea how old they are. They're probably due for a change as well.
I'll pick up a hall effect today and give it a shot. When I had the cap off for a look it is pretty "green" looking in there.
Well I changed the hall effect today, and it doesn't seem to be any better. The idle MIGHT be a bit smoother, but it still doesn't want to start without either priming it, or cycling the key 5 or 6 times.
I checked the timing with the coolant sensor unplugged and it was at about 15 or 16 BTDC so i set it back to 10.
I checked the injector pattern with a flashlight, and it doesn't look that great to me, but I'm not sure what to look for. I see a fast pulsing "cone" shape flow, but I also see obvious bigger drops just dribbling out of the injectors.
I still need to check the fuel pressure, but now I'm thinking it must be a weak fuel pump.
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