95 Riv eating fuel pumps like candy.

Hi all,

Here is some back ground. I replaced 3 fuel pumps before I realized that the fuel regulator was clogged with crud, a lot of crud. I cleaned all the crud from the fuel rail and replaced the fuel regulator. The fuel pressure was around 40 psi. After the new regulator at idle. Car ran put not good. The next day the 4th fuel pump died. By this time the shop that I’m getting the pumps from doesn’t like me any more and will not warranty the pump. EBay here I come. I got just a new pump off eBay and put it in Friday morning after I got home from work. I only have 35 psi at fuel rail at idle. Car runs put not good. I checked fuel pressure at the pump, after the fuel filter (new last week) and before it goes in to the fuel rail and they are all at 90 psi. I then pulled the return line off the fuel module and I’m getting a lot of fuel on the return line, fuel regulator must be bad. I called the part store for a new one and found out the first one was for a 96 not a 95. Got the new one Saturday and put in on and the same thing 35 psi at fuel rail. Now here is the funny thing. I can pinch the return line with pliers and the fuel pressure on the fuel rail will go up. Is the fuel regulator bad again?

Is your car modified? How long have you owned it? is is daily driver or did you "rescue" it from a barn/garage/yard?

Reason I ask is it sounds like you have problems relating to the car having sat a while.

I wonder if you were aware that a factory scan tool (Tech I or Tech II) or close equivalent with 2-way communication lets you "command" the pump on and off for diagnosis. I mean, you can use a small jumper to hotwire the pump, but if you had the tool you could turn it on/off from the drivers seat or while you're working under the hood. So for instance you could flush the fuel system by disconnecting the right connections, guiding the fuel in the appropriate receptacle, til it runs clear or tank is empty. Also you probably noticed that the tank is plastic and doesn't weigh that much, and you can still get new straps to put it back up when done.

The third thing is I wonder if you have or have access to the service manual. If not, it appears you'd benefit from a service manual set for your Riv. They are relatively cheap on eBay, usually around $30, although you may have to look for a few days (really, just a few days) to get one. The manual would explain a bit about how the fuel sustem works so you could plan your troubleshooting accordingly.

Why?

- the car running but not running well is not necessarily a fuel pump problem. The manual would point out other places (ignition) to look, which will benefit your troubleshooting.
- if you are asking why the fuel pressure at the rail goes up when you block the return line, you may benefit from reading up on how the pressurized fuel system works and what the pressures are supposed to run. You *should* be getting a lot of fuel on the return line at idle. The manual woudl explain this, which would benefit your troubleshooting as well. The manual would explain that when you are idling the fuel pump provides fuel at pressure to enable the car to accelerate and the excess pressure is bled off and fuel returned to the tank. Part of the benefit of the return is it tends to mix the fuel and prevent a buildup of water from condensation and such.
- I wonder why you had the series of fuel pump failures. For instance, if you have silt in the tank that was jamming the fuel pumps. What do you think? Finding the root cause would give you (and us) great clues as to how to fix.


What do you plan to do next?

Are the pumps completely failing or whining or what?

35 psi at idle sounds about right or maybe just a hair low. Do you have a mighty vac? If not, you could remove the FPR and do a "suck test" on it.

* Locate FPR at end of fuel rail.
* Identify small vacuum hose from top of FPR to Intake Manifold; disconnect tube from intake manifold, and inspect for cracks, leaks, poor connection.
* With engine ‘off’, a mechanic would use a Might-Vac or similar vacuum tool to suck on the tube against the FPR.
* The FPR *should* ‘hold vac,’ about 14 psi; if it doesn’t, then the diaphragm has failed and a new FPR is in order.
* In the absence of a Mighty-Vac, use your lips to suck on the tube against the FPR; again, it should ‘hold vac’, like sucking on a soda straw with your finger over it.
* There will always be a *slight* odor or taste of gasoline present, which is of no concern.
BUT, a ruptured diaphragm will allow a slug of raw gasoline thru the tube and toward your mouth, which becomes quite unpleasant; use a rag for mouth protection, or use some clear aquarium tubing in lieu of the stock vacuum tube, so you can see approaching gasoline.

I bought the car almost two years ago; I rescued it from a yard after setting almost two years. I drove the car daily (80 miles round trip) with no problems for six months before giving the car to my son. All the crud in the FPR looked like rust. I cleaned all the rust out of the fuel lines and the tank and changed fuel filter. Two of the four fuel pumps froze up and the others the pressure dropped to 20 psi. I do have a Might-Vac and the FPR is holding vac. Car has a very bad hesitation when fuel pressure is at 30 psi and 40 psi (when driving). With return line pinched and fuel pressure up around 60 psi no hesitation when driving.

Scratch it runs good with the return line pinched so there is 60 psi on the fuel rail. My son said he did this put he didn’t understand what I wanted. I pinched the return line when I got home so there was 60 psi on the fuel rail and the car still ran bad. Going to look at the MAP and MAF sensors. I have no engine light on.

What reading are you getting at the fuel pump with ignition on and engine off? Do you know what brand pump you have in there?

I have 40 psi with ignition on and engine off and around 33 psi at idle, this is the reading at the fuel rail. I'm getting 90 psi right out of the pump. The pump came from High Flow Fuel Systems. I unpluged the MFA sensor and the car ran the same put had a higher idle. I can not find the MAP sensor to unplug it.

If your car is supercharged your car does not have a MAP sensor. If it was not supercharged, then it does. 95 was a weird year. 96+ all do have them.

If there was crud in the FPR and rails, your injectors are likely really bunged up. Each injector has its own filter, too. If there was enough stuff to qualify as crud to be cleaned out of the rail, its logical to assume that the injectors need repair too. Where did all the crud come from? was it run without a fuel filter? is the fuel filter membrane broken?

No idea how long the filter was in the car before I got it. Replaced the filter after I got the car because I had to repair the fuel neck overflow tube (it had rusted away). I have also replaced the filter every time I put a fuel pump in the car.

Those numbers are a little low. You should be getting 48-55 with the ign on and enigne off and 3-10 psi less at idle. Just a guess but it could be an obstruction in the line. Something like that can be hard to properly diagnose.

Have you taken these readings to the local shop and talked to them about it? I'm with Albert on dropping the tank and seeing whats in there.

01roadstar wrote:

No idea how long the filter was in the car before I got it. Replaced the filter after I got the car because I had to repair the fuel neck overflow tube (it had rusted away). I have also replaced the filter every time I put a fuel pump in the car.

AHA.

Your smarm probably has come from whatever washed down the fuel filler tube before you replaced it. And there is probably a lot of it in the tank. It only takes a small amount to wrack your fuel pumpand the finest grit would pass the filter and get to the injectors (that is why they have screens and the rail clogged up)

Toobad it's not safe to vacuum out the tank. Yeah, I suspect you're going to have to drop it or take it somewhere to be dropped, drained, cleaned and reinstalled, Until you do you're just going to be sucking scale out the tank bottom and killing pumps. A rusty filler can put a LOT of debris in the fuel tank. And the more it rusts before failing the more silt you get. It's like a little portable crud factory once it starts to go.

Do you think you also may want to take the fuel rail apart again and clean it out too or at least check it, and check/clean the injector screens. After dropping the tank and cleaning it out that is.

If there is any good news here it's that with a new filler pipe and such, once you fix the source of the problem (debris in the tank) this won't likely recur.

I wonder what the PO was thinking when driving the car so long with the CEL on. It likely was on becuase if the fuel filler rusted thru the EVAP system should have set a code. Maybe he/she just did not want to or could not fix it. Or lets suppose the CEL did nto come on - the filler was not perforated by rust. But under the right conditions it would not surprise me that the inside of that tube became rusty -- filling the tank bottom and then the fuel filter with a fine grit. Which would get forced eventually thru the filter and beyond.

And this may not fix your entire concern but is necessary to make some headway on it.

And given the fuel pressures you are seeing I wonder if there is still debris (a fine silty mud of sorts) in the FPR and such.

All,

Pulled the fuel rail and done some good cleaning and car is running fine. We took it out and make some tire smoke. The son want's to start looking for a 98 or 99 riv when he come's back from bootcamp, SUMPERFI!! He want's to make a 13 sec. car out of it.

Thanks for all the help.

Murray

01roadstar wrote:

All,

Pulled the fuel rail and done some good cleaning and car is running fine. We took it out and make some tire smoke. The son want's to start looking for a 98 or 99 riv when he come's back from bootcamp, SUMPERFI!! He want's to make a 13 sec. car out of it.

Thanks for all the help.

Murray

you are welcome --but what about the tank?

The tank is clean no rust no nothing.

Thanks,

Murray