94 RM Estate Wagon fuel pump
 

Can I ask if you were able to do any checks to confirm it is the fuel pump itself when it could be a blown fuse?

Something to consider;if the fuse and relay check out OK and it is the fuel pump.



Circumstances being what they are, you just might get one more chance to get the fuel pump working so you could have the vehicle where it is more convenient to tow or drive.

There have been times when a rap on the bottom of the fuel tank, with a rubber mallet, while the engine is being cranked, got the fuel pump running. This only works once, but would give you the chance to move it under it's own power.
Of course you must be very careful , so the vehicle cannot move while someone is under it, so make sure it is in park and the parking brake is applied before attempting this move.
I t will usually keep running, until you shut it off,then doesn't work again.

There is a port to check fuel pressure on the fuel rail. If the pump is silent, it is 95% chance that the pump is dead. I would check the relay instead of buying a new one. A VOM is your friend. You only need to buy a pump, not the whole assembly. Buy an AC Delco, Delphi, or Walbro pump. Do NOT buy a Bosch. The pump should cost about $75-100. Check Amazon and ebay.

You must drop the tank to replace the pump. I have found places that will do it for about $100. There are three lines, two nuts at the front, and two bolts at the rear. There are two different ways to handle the filler neck. I prefer to unbolt it at the top and remove the left heat shield so you can lower it attached. This way you will spill less fuel. You can remove it at the tank, but the likelyhood of a fuel spill is much higher. There is also a ground strap on the filler tube. The connector is at the rear left on the frame. While you have the tank down, replace the vent line to the metal vent line on the filler tube. It is 18 mm fuel line. You can use 19 mm (3/4 inch) if you tighten the clamps sufficiently (you can not get the hose on a weekend). The hose is one of the possible leaks that can be prevented. You may need a quick release tool for the fuel and return lines to the tank. The lines are held away from the suspension by a clamp wire on the body above the axle.

If you can put it on jack stands, you can disconnect the hose at the back of the fuel filter, and siphon the fuel into container below the tank. It is a lot easier to remove and replace when empty.

Hitting the tank on the bottom can get the pump to run. You may even get a couple of responses to that. It may even start a couple of times.

For what it is worth,


Some GM fuel pumps were fed power through the oil pressure switch. If you do not have power to the pump it might be a good idea to check that switch.

Thanks for the updates.

There should be a dangling connector near the fuse box post. It is the pump override connector. If you connect it to the battery positive side, and the pump is good, the pump will run.

$230 sounds like a lot, especially if you supplied the pump and sender.

There are a few things to keep in mind.
If,,,,,,,everything is pretty rusted under there and possible exposure to road chemicals the job can get to be a bit of a hassle and the addl cge may not be out of line.


Some places will not warranty a job if the owner supplied the parts, it gets a little tacky at times.


The pleasure of driving a very comfortable car will be worth it.

Glad all is well, thanks for the update.

There is a product from NAPA that is called Anti studder. It goes in the trans. It will stop trans studder, but if that is the issue, you are probably going to have a trans rebuild in the near future.

Could what you describe as shudder be a possible misfire condition or power being cut as cutting out?
It could be either fuel or electrical , something like a fuel pump relay dropping out resulting in a fuel problem.

With older vehicles you had to use some imagination and place a fuel pressure gauge where you could see it while driving or a test light in the right place to see if signals were dropping out.
It will be interesting to see what the shop comes up with.

The condition usually occurs at low throttle settings, in high gear, and at those speeds. I though it was a misfire, but when I added the anti studder, it immediately quit. If you shift into a lower gear, it will usually stop as well.

Fuel pump relays have not been known to produce that symptom. Fuel pumps usually work or do not work. It is possible that the ignition wires are arcing. You can check for that at night...there will be a light show under the hood.

Are you putting Reg grade fuel into the tank, if so , before adding anything suggest you try 1 or 2 tankfuls of premium grade gas.

Car will run OK with Regular, but premium leaves less deposits and usually will clean the injectors.

Just a little side note,
I would ask about the warranty, are you required to bring the vehicle in any particular times for what kind of service for the warranty to be honored?
I believe you are doing the best thing by getting different estimates and being aware of the fine print in any warranty.

If you are getting the parts you noted, the price installed does not sound all that bad. I had my trans built to take 500 hp. It cost me about $1400 without installation, another $500 for the 2400-2600 rpm stall torque converter, and 12 quarts of trans fluid. Due to the nature of my installation, there was no warranty on the one I bought. Depending on the installation costs in your area, they are not far off.

Update. The car has been back to the shop three times for poor surging idle and lack of power on kickdown. We replaced plugs,Opti, water pump, Opti vacuum line, both O2 sensors, repaired vacuum line to the EGR valve, new left Cat, right is ok.

We fixed the lack of power, turns out the wires while they tested good were breaking down under load. Coil wire showed evidence of arcing to the metal protector. The surging idle still remains a mystery. I was sent the GM shop manual for just the LT1 motor and it’s about 1000 pages long. Extremely detailed. Even so we still have not isolated the problem. Ironically after changing wires the left bank was rich now it switched to to the right bank rich. No reason.

So we are going to try to try again Monday. I’m awfull close to putting a nice Holley carb on this car.

My el Camino with a carb sat for 6 months, never looked at it. It spun over a few revs then started and purred like a kitten.
it drives like a new 42 year old car.

If anyone can offer suggestions please please do so.

As you are probably aware by this time, an over rich condition on whichever bank will destroy the converter on that bank.
The O2 sensor is supposed to report the exhaust oxygen for their respective bank. Now, if there is a rich condition for the right bank the list of what can cause that needs to be checked out.
Has anybody checked the exhaust for any restrictions? The converter on the other side may need to be replaced now..
Either the shop where you are having the work done is guessing or they just don't know what to check. Maybe they just don't have the equip .
After reading all the posts so far, could you possibly make a list of what was replaced. When you look at the list you might agree with my conclusion about guessing.
If you would , they obviously have connected a scan tool to get the various data readings.Ask for them and post them here and we may be able to put forth another point of view. What do you think?

My post right above shows everything that has been replaced. This shop agrees with my philosophy of not just throwing a bunch of parts at it hoping to cure the problem somehow. Each item that we replaced was for a detected failed item with exception of the right side O2 that I felt should be replaced simply because we replaced the left side too. We did the scan the right side before and after and it shows the O2 operating correctly.. my choice of throwing parts.

BTW, all items are to be OEM GM stuff. Absolutely no MSD or auto store brands. I’ve been burned too many times This car is an old people car, as such it should function near perfect everyday even if great grand ma takes it to sewing circle or great grand pa takes it to senior discount breakfast with other octogenarians. I’m not quite that old but dam close. I’m fortunate enough to still be able to roll around on a creeper or bend over a fender.

My 42 year old el Camino runs exactly this way, so it’s son this 25 year old kitten should too.

yes early on we checked the exhaust by simply disconnecting both pipes and addinding a short extension on each side. This is how we found the left Cat was bad. Going forward we found all the plugs black on the left bank. Why? Plug wires looked good, nice and flexible, came off the plugs correctly. Then we found oil around the Opti. And the vacuum line was deteriorated. It’s not exactly a screwdriver and you pop the cap off operation. So we did pull it out along with the water pump. The big oil seal was leaking badly and had soaked the Opti insides. That’s when we replaced the Opti, the oil seal and the water pump. Also installed a new vacuum lin from the Opti. This is the second gen Opti some don’t have this feature. This fixed the rough running and most of the misfire. We also cleaned and inspected all the related wires and connections.

interestingly I’ve been to 5 very popular shops other street rodders frequent. None have good experience with this OBD1 and none had scanners good enough to really read the system. Some shops have not even been around since these LT1 were created. I swear they all are bolt on freaks and when it comes time to create and delve into how these systems work they are lost. I asked about fuel trims as a test. I got ??? WTF is that?? If their equipment can’t even get to the point where these can be seen they really are just guessing. They all told me it’s not possible to scan this deep. You can’t without top notch equipment.

Our last scan scan shows everything operating within range. The richness on the right bank is right at the top of the scale while the left bank is below center of the range. There are no codes showing on the more or less standard code reader. The average shop would blow me off as nothing is wrong. Why hell does this car rock and roll like a pro mod then? My supercharged Willys did not do this., and if any car would it should have.

So electronically it seems ok. We have checked for vacuum leaks and replaced virtually every piece of hose on the motor. The air intake duct hoses are smooth and not cracked, all the hose clamps are tight. We tested by wiggling the air intake stuff as though it were on a rough road and no motor operation changes occurred. We have wiggled about everything movable and nothing is affecting operation.

This issue comes and goes. One day the car is smooth as glass, the next day same road same stop lights same traffic it idles like a junker. It doesn’t matter outside temps have been -20 to + 80 rain shine or blizzard. I’ve tried full tank of gas to near empty, both standard 87 and non oxy premium 91. I usually go to one of three stations, all are very high volume stations so no back road month old gas.

This problem is not unique. There are many LT1 posts in other Camaro and Corvette forums covering the same issues. I’ve yet to see a definitive solution. We’ll fix it I’m sure.

Looking at this from an engineering view...I am one of those geeks, retired, GM was way ahead of the game with this system.....when it works. It’s capable of very close air/fuel management matching engine and road conditions. Many of these have been modified with good results. There are re-programmed computers for these. I’m not about to even consider this until I can see a problem with the existing one. It may already be there, we just have not got that far yet.

Other than the messy idle the car runs great. I’ve averaged around 20 mpg all winter. Highway speeds are ridiculous in the morning rush hour. 75-80 in the left lane. I drive nearly 50 miles each way so it get a good work out.

Monday we’ll be back at it. That monstrous manual is hard to page through on the computer. I wish it was a paper book.

Sorry for the long post, it’s been a long hard winter.

Thanks for the reply.

OBD l required the tech to do the detailed testing manually.
OBD ll does it for you. What you need is a retired tech who is looking for a way to not let his/her valuable experience go to pot.
Can you obtain those multiple read outs and post them here?
Things like oxygen cross counts, voltage readings , coolant temp, RPM, Idle Air Control, Fuel trim (if under 128 or over) is required to know as is injector on time .
Grant you all the parts were OEM , but sometimes they were questionable and it required the tech to know how to check the system and what it was supposed to do.
There was no such thing as "Freeze frame" with OBD l and the scan tool had a feature described as "Road" and those results were indicative of what the conditions were at the time the system was malfunctioning., but the tech had to be watching the readings at the time. I hope I might be able to offer some assistance, but we do the best we can.
Since you have the manual, and you like to read, it's April now and maybe in July, or sooner, you will know what you want to check and how.
You know more about this vehicle than the people you are taking it to , so don't be shy asking them questions. Sometimes a question will open another pint of view and hopefully more ideas will help pin down the problem(s).
Can you get them to scope the crank and cam sensor waveforms and watch them later when they /you bring it back off the road test?

Thanks for the info.

we got the down shift issue fixed. Plug wires arcing to the protectors. The trans works great.

We have had issues getting the expensive tool supplier scanners to work properly. Without this you are just guessing. There are no codes showing on my car yet it runs terrible. The car only has 115 k on it and no winters except this one.

we have the EEHack software but ran out of time as I needed the car for a couple Doc appointments. I’ll bring it in next week again.

Its too bad that I don’t have a place to work on cars anymore or I’d be more into it myself. I don’t have a laptop anymore but I could get one then I could have running scans.

yeah, I know OEM stuff is not without faults but aftermarket stuff is worse by a long ways.

The switching of sides AFR is puzzling. The only thing that was changed was the O2 sensor. We’ll try and put the old one back in and observe what happens. That was my call....throwing parts at a problem that doesn’t exist. We’ll see.

The nice thing about the EEHack is that you can save a scan and look at it.