I have a 94 ram 1500 with a 5.2 my son was driving it and it died on him we poured gas in the intake and it started but will not stay running so spark is not the problem. Checked the relay, fuse, and power to the pump and they all worked fine so we replaced the pump but it still wont start. Would appreciate any ideas thanks.

 

Check for correct fuel pressure at the fuel rail. Not sure what pressure is correct but I'm sure you can find that info here somewhere. If pressure is low or non existent it could be a clogged filter. The could also be the possibility that the new pump is defective. Just a couple ideas for you to look at.

 

Spent all day yesterday replacing the fuel pump TWICE because that is what i thought it was to a bad pump. I'm not a mechanic but I'm not an idiot and I know the pump is in right whats the odds on two bad pumps. What do I use to check the fuel preassure ?

 

I know this system inside and out. Let me help you.

Here's how the system functions:

At time of KEY <ON>, power is applied to the PCM which in turn powers on the ASD relay. It's in the Power Distribution Center (PDC) located on the driver side fender well. In this case, it is getting spark so, we can factor that out as if it were dead, it would CUT power entirely to the EFI system which, in turn, would CUT POWER to the ignition CKT (circuit). Since you've verified it has spark- we can factor that component out.

NEXT:

FUEL PUMP RELAY and FUEL PUMP FUSE

Also in the PDC, there's a relay for the fuel pump. This relay MAY be faulting thus, no power to the pump is measured.

TO CHECK: have someone turn the KEY <ON> and listen for the pump motor by placing your head at the fuel pump / tank area. You will hear it energize and spin for ~3 seconds with the KEY <ON> event. It will then auto shut down.

<IF> you hear it- you know it's getting power and, we can factor that relay out. However, there's also an electrical test. You will need a DMM / OHM meter to perform this test. If you'd like more information on HOW, just let me know. But, this should provide you with enough information to make a decent assessment of the situation without electrical testing and meters.

<IF> you DO NOT hear it, NO POWER is being supplied to the pump.

<IF> NO POWER: you now know that either the FUEL PUMP relay has faulted OR: THE SUPPLY TO the FUEL PUMP relay is not there.

There also is a Fused CKT that I believe feeds the fuel pump. Look for a 20 A FUEL PUMP FUSE that's blown IN THE PDC.

Start there first. Let me know how you make out with that.

EDIT: To answer your question regarding HOW TO MEASURE FUEL PRESSURE:

You will need a fuel metering device such as a PRESSURE GAUGE.

This will connect to the Schrader Valve at the rail (NOTE: depending on the year, some models DO NOT have a test port).

Simply place a rag over the opening of this valve and press the valve to release pressure.

NOTE: It's not a huge pressure and, gas is not going to spray all over the place. Just place the rag to soak up the fuel so that it doesn't end up on the motor or get in your eyes.

Screw the end of the pressure gauge into the port - HAND TIGHT ONLY.

Hit the KEY <ON> one time for 3 secs and KEY <OFF> *Key off disables power- safety here.

Pressure SHOULD READ ~49 psi ± 5 psi NOTE: Older models had a different spec and, I believe it was 95 and below that were rated at 36 psi same tolerance.

IF pressure does not come up on the first try, turn KEY <ON> once more. If not, one last attempt should do it. If not, there's an issue.

Normally, pressure comes up first time UNLESS, the fuel supply system has been totally replaced thus, all lines are empty and filled with air. Under normal circumstances, the lines are filled with fuel and instantly (within a sec) up to opertating pressure.

CM

 

I have checked the fuse checked the relay and used a test light at the plug that goes into the pump everything seems to be working. when the key is turned I hear the pump start up and then shut off as it should. I checked further down the gas line before it goes up to the throttle body and gas is there, is there something between where the line goes up and it goes in to the intake that could be blocking the fuel. If I press on that place you said to check preassure it will let out a little air but no gas it does not seem to have much preassure at all.

 

I can get it to run if I pour in the gas now it will stay running for 30 seconds or so if I keep it at about 1000 to 1500 rpm then it sucks air like crazy and dies. Any ideas.

 

Go to your local neighborhood parts store, and pick up a 'noid' light. Unplug one of your injectors, and plug it into the noid light, crank the engine, does the noid light flash? (they are only a couple bucks.)

 

Even easier and not needing a NOID light (electrical check only) is to simply keep it running and, using a long handle pry bar, place the steel end to the injector body at the metal seam. Then place your ear up to the handle- if you don't hear any clicking- they are either not being powered on or are mechanically not working- either way, an absence of fuel is seen at the intake. Now, since you've got 6-8 injectors, if one is not working, chances are, there's no power to them. The injector driver CKT is dead. This is rooted at the PCM hardware level and, it could either be one of two electrical related issues:

1. There may be a ground fault for this CKT (circuit) OR,

2. The control driver CKT at the PCM may be faulting thus, it's not switching the grounds. BUT, EVEN IF THAT WERE TO BE THE CASE!- that still does NOT explain the absence of fuel at the rails. In my opinion and, after mentally mapping this out, this is our root failure mode: NO FUEL CONDITION. That's what I would be focusing on. I would be asking myself WHY would no fuel be witnessed? Then, based on what I know about this fuel system, I would be writing down some tests to root / factor out possible root causes.

BUT: something you had stated was: no fuel is / was present at the Schrader valve and, that makes me stop and think. I also noted that AIR was being displaced out of the valve which, leads me to believe it's not pressurizing the system up to that level. That pressure (that was low) was the expansion pressure of the system. As the ambient air temp rises, so does the internal pressure in the fuel lines.

Moving on to your questions:

To answer your question: The answer is NO- not in that area that you're looking at. Yes at the PUMP inlet (I know, this is a new pump but, let's walk the path) it will. But, HIGHLY unlikely down the line UNLESS, you've got cold rolled steel lines that have rusted shut at the fitting / mating junction.

When coming out of the pump, we have a hard line or, on your year- (stopping to think first and check my manuals) you may have either steel or flexible tubing for supply lines. My manual does not say but, in recent past year on here, it was only used on one year and then it was designed out so, I think you've got steel lines.

In either case, they are not likely to plug and though the steel ones do tend to rust like mad at the fittings, it's not going to plug the line. But, on SUPER rusted fittings, growth and deposits and debris can build up. I've seen PICS of this but, never witnessed this condition myself.

It sounds like the problem is rooted around NO FUEL being delivered up to the rails.

I want you to do something. I want you to run a simple test.
- remove the line from the fuel pump. NOTE: There's a simple, quick connect fitting, press in both ears and slide it off the pump. Gas is going to come out so, FYI on that. RAG TIME there.

-Place another tube on that fitting and run it into a clear glass container or suitable FUEL resistant. ALT method: wrap a rag around the output.

-KEY <ON>

-THe question is: do you see fuel coming out? ALT: is the rag soaked with fuel?

-----<IF> YES- we know the pump is working and, now, to find the plug and / or kink, leak etc further up the line.

---------<IF> NO: this means the pump is not working and, we need to find out why because, after installing a new pump, it should be.


Now, the next thing is that the line comes up the side (drivers) side underneath and mates to a quick disconnect fitting that is attached to what is called a FLEX LINE.

The flex line is SS-braided (depending on model) or, can be flex TUBE which, is usually made of PTFE (or equivalent) on the inside with SS braided over along with a protective black sleeving.

The flex line mates to the fuel rails at the inlet. There's your flow diagram ok.

Knowing that, you've got THREE points to check and they are:

1. Fuel pump outlet

2. Fitting at the flex line below driver door / firewall line

3. Flex line to fuel rail

Each one would be removed one at a time and KEY <ON> to test for flow.

Walk that path. You can either start or end at the fuel pump. I always start at the pump as the probability is much greater of failure at this level than in the engine bay and line level. This way, you root out the failure quicker. However, it is real world testing and, it could be an odd ball anomaly.

Start with that and report back. Oh, I HATE to ask this question as it may offend you but, please have mercy on me for asking this:

Are you sure beyond a reasonable doubt that the fuel tank is NOT empty and that the fuel gauge is not stuck? I've had that happen 22 years ago and, as embarrassing as this is to admit, I was almost to the point of pulling the engine before I came to my senses and stuck a stick into the tank. Yeah, it was bone dry.

CM

CM