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not getting fuel??

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not getting fuel??

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  #1  
Old 12-03-2018, 02:02 PM
jtarrington
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Red face not getting fuel??

Have a 98 ram 1500 that seems to still not be getting fuel. Some insight: Was driving on the highway about 65 when suddenly lost power. Got to the side of the road and it will turn over but not start.
Now I have checked the fuel relay AND replaced the pump. A friend believes it could be related to the ECM, but I still don't hear the pump prime when I turn on ignition. Looking for advice before I keep buying parts and not solving the problem.
Thanks!
 
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Old 12-03-2018, 03:11 PM
wrnchbndr
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I have a '97 and I have never actually heard the pump as people say you should listen for. I'd just go straight for the real test and see if you have fuel pressure. Lots of folks just start swapping parts in situations like this. Rule #1 should always be to not fix something if it isn't broke. If you don't have fuel pressure, have a look at the wiring diagrams that supply the fuel pump. The ECM (or PCM) is involved in the activation of the fuel pump but there is also the Automatic Shutdown Relay (ASR) that can also interrupt the operation of the Fuel Pump Relay. The way I read the diagrams is that the ECM supplies the ground for the fuel pump relay and the ASR provides the 12V for the Fuel Pump Relay. You need both the ground from the ECM and the voltage from ASR for the Fuel Pump Relay to activate the fuel pump.
 
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Old 12-03-2018, 03:29 PM
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Originally Posted by wrnchbndr View Post
I have a '97 and I have never actually heard the pump as people say you should listen for. I'd just go straight for the real test and see if you have fuel pressure. Lots of folks just start swapping parts in situations like this. Rule #1 should always be to not fix something if it isn't broke. If you don't have fuel pressure, have a look at the wiring diagrams that supply the fuel pump. The ECM (or PCM) is involved in the activation of the fuel pump but there is also the Automatic Shutdown Relay (ASR) that can also interrupt the operation of the Fuel Pump Relay. The way I read the diagrams is that the ECM supplies the ground for the fuel pump relay and the ASR provides the 12V for the Fuel Pump Relay. You need both the ground from the ECM and the voltage from ASR for the Fuel Pump Relay to activate the fuel pump.
Thanks for replying. I am getting pressure from the new pump since I've installed it. The ASD relay seems to be fine and I put my own ground on the PCM just to see what would happen. At this point it seems I'm just not getting spark, but I have no idea where to start with finding the culprit. As you said I would like not to keep just throwing parts at it, but my knowledge is somewhat limited.
 
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Old 12-03-2018, 03:42 PM
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*Update*
I got it to run for a couple of seconds using starter fluid (granted very rough) but would that eliminate not getting spark?
 
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Old 12-03-2018, 04:49 PM
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Three requirements, Fuel, Spark (at the right time), Compression. A can of worms on modern vehicles...
Actually just the opposite. "Runs with starter fluid" is actually an indication that you are getting spark. But lets qualify that by saying that "you are getting some spark". You might not be getting consistent spark or a strong enough spark. Its common that problems like this can be caused by "intermittent" malfunctions and using starter fluid to diagnose problems isn't really a definitive thing. I feel your pain as I just went through a similar type of problem myself. There's a ton of stuff that can cause what you describe but I will say that you're on the right track by being cautious and not coming to conclusions prematurely. If you were watching the fuel pump pressure while you were starting the engine and the engine would not continue to run when you tried the starter fluid you have ruled out the fuel pump as a problem. I'd also say that you've ruled out compression. But there still is the possibility that you have a fuel related issue or a spark related issue.
Its difficult to diagnose a problem like this due to the complexity of the modern engine. The most direct approach is to take the truck to a diagnostic center after you have thoroughly inspected all of the electrical connectors under the hood. Gently disconnect the connectors once you have determined and understood how they are designed to come apart. Look for pushed pins and damaged wires. Spray the pins with contact cleaner, let them dry, and reconnect them one at a time.
I highly recommend learning the reputations of local mechanics who own their own business. Old school mechanics who have stayed on top of the technology changes are the best.
 
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Old 12-03-2018, 10:06 PM
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Next thing to test is, are you getting injector pulse. You can buy/rent a noid light from most of the big chain auto parts stores. In a pinch, a simply test light will do the trick.
 
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Old 12-04-2018, 12:27 AM
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Starting to check connections and obvious wiring issues was the next step I took in finding the culprit to no avail. I took an ecm from a buddy of mineís 00 just to see if it would make a difference. I wasnít sure if a different year was compatible let alone the his being the 3.9. But, it did start although ran terrible. So now I believe Iíve narrowed it down to the ecm. What route should I take in buying the replacement if you guys would have any suggestions?
 
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Old 12-04-2018, 10:14 AM
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I am surprised the 00 PCM would even run the V-8, there were a LOT of changes between 97 and 00......

There is a company that sells replacement computers that is a sponsor here on the site. Look 'em up.

Although, given that your truck IS a 97..... You can get a PCM from the junkyard, 96-97, with same engine and trans, and it will be plug and play.
 
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Old 12-04-2018, 11:27 AM
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Originally Posted by HeyYou View Post
I am surprised the 00 PCM would even run the V-8, there were a LOT of changes between 97 and 00......

There is a company that sells replacement computers that is a sponsor here on the site. Look 'em up.

Although, given that your truck IS a 97..... You can get a PCM from the junkyard, 96-97, with same engine and trans, and it will be plug and play.
its a 98, but would a 97 be plug and play? Iíve been having a hard time tracking one down locally. Iíve talked to every salvage yard within 40 miles of me. Iíve looked at a few options for ordering new replacement computers, but Iím looking for cheaper alternatives in the mean time. Itís a workhorse truck that I mainly using for carrying material or debris to/from jobs. Iíve been searching the exact part number from the ecm I removed but Iím not sure to what extent they are interchangeable as far as other years with my same setup. Anyhow thanks for all the advice. Iíd probably still be pulling sensors if it wasnít for this thread and some others I read through!
 
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Old 12-04-2018, 11:30 AM
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I'm very surprised myself and would never suggest or try doing what you did. I'm interested in the "Noid Light" mentioned by HeyYou for testing injector pulses. Is it anything more than a conventional test light? Could you post a link to what you are describing from someplace like ebay or a parts supplier? I have in my possession a type of spark tester that is installed in line to the spark plug. Its valuable because you can visually see that the ignition system is working with the spark plug installed. They're not a definitive test of the ignition but they are easier to use when you're by yourself. Unfortunately they require spark plugs that have a removable screw-on contact.

If you can find a used PCM from a truck of the same year and engine size it might save the day but I still think there is question that your PCM is the problem. Understand that this is a forum where people congregate with truck problems. Bad PCMs happen but they are not common. The fact that your truck started at all with a PCM from a 3.9... If you're going to look for a PCM, try to find someone parting out a truck on craigslist due to an accident. PCMs can be expensive and large operation junk yards know what they can get for these.
 
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