The Truckster Log

Hello everyone I wanted to start this log to document and share the progress of my 1994 Buick Roadmaster Estate. First a little background, I have always liked wagons like the SRT Magnum, CTS-V wagon and the 94-96 Impala SS. I never knew much of these B-Body wagons. My father in law was the previous owner and about a month ago it started giving him problems such as loss of power, hard starting and the engine shutting off randomly. He had spent money on some repairs previously and grew tired of it dealing with the wagon. I am an ASE certified mechanic so he asked me if I can help him look for a replacement mode of transportation. After we found his new car he let me have the wagon. That is how I came to be a wagon owner. After researching this platform I have come to love it.

The wagon has about 181000 miles and could use some TLC so the plans for the Wagon will be broken down in 3 Phases.

Phase 1 - Get the Wagon running and dependable which will include repairs and maintenance to the engine and drivetrain. It needs some exterior trim items replace and the interior needs alot of help. What I have seen so far are torn seats, drooping headliner, drivers door panel held together with tape, broken and missing trim, radio buttons don't respond and rear tailgate only swings to the side. The interior could also use a very deep cleaning.

Well I'm looking forward to the journey. I hope you'll follow along.

Getting on with the first part of Phase 1, I proceeded to diagnose the trouble and while the infamous Opti-Spark is usually the first to be blame I decided to first check for a vacuum leak based on the "repair" made to the homeplate.





After spraying carb cleaner and inspection all the vacuum hoses found nothing wrong. Next I decided to check the fuel and found the following.


This was the pressure on initial KOEO:



Pressure for KOER:



Pressure with regulator vacuum line disconnected:



Well seems that the fuel pump is going out. I decided to replace not only the fuel pump but the fuel pump housing and level sender, new regulator because of age, fuel filter and perform an oil change. I bought the housing from Rock Auto and it seems that this is for a sedan since it has a short pigtail compared to what the wagon comes with. Something to keep in mind if you decide to purchase this part.

In my pervious post you may have noticed the repair done to the homeplate but this is the repair done to the oil fill tube causing a leak on the passenger side valve cover. The threads on the valve cover look stripped and my oil fill cap is a quarter turn close style so I will need to find some solution. I will be adding a cold air intake so not really worried about the homeplate.




The coolant tank appears to have a crack that was epoxied and hasn't been leaking but will need to be changed out for dependability reasons. I have heard replacement tanks are a hit or miss, luck of the draw situation. Just need to find a good replacement, any suggestions?

Congrats on the new wagon. They are great cars.

You are correct, the sedan and wagon require different sending unit assemblies. Stay far away from the Delphi unit you see on Rock Auto, Advance Auto, etc. The hose between the pump and top plate is made from rubber that is NOT rated for fuel submersion. It will quickly swell and burst, leaving you stranded and angry.

Aside from that it is a good unit though and can be had for cheap from Autozone. They even offer next day delivery. once I realized the hose was the issue I swapped it out for a piece of corrugated line like the Delco part in your picture has. It went right on and has been trouble free.

As for the coolant reservoir, I got a cheap one from eBay and it has been great so far.



Good job on the actual troubleshooting instead of blindly throwing blame at the Opti.

some 'interesting' repair work you are fixing correctly.

The Opti could probably use a new cap and rotor and maybe plugs and wires too...


looks like his tank has two small hoses on it, what's the difference between that and the ones with only one small hose?

I have a couple of pressure tanks $25 plus shipping. One is for a 96, and one is for a 94/95, but I think the second port is closed off.

rcktpwrd wrote:

some 'interesting' repair work you are fixing correctly.

The Opti could probably use a new cap and rotor and maybe plugs and wires too...


looks like his tank has two small hoses on it, what's the difference between that and the ones with only one small hose?

The 94s and early 95s had a hose that ran from the tank to the top right corner of the radiator. It was eliminated at some time during production of the 95 model year. Mine was made mid Dec 1994 and only has one hose.

If the old sending unit was reporting fuel level correctly or close to it I would just replace the pump, I've had 4 different sending units in mine and only the original was accurate, the rest are all off by about a quarter of a tank, so the gauge will say I have a quarter tank left when I will actually have almost a half tank.

there are several you tube vidoes of people rehabbing their old GM sending units which is usually just cleaning up the resistor that the end of the float arm rides on.

Updating my progress on the wagon. Well, as mentioned before the main issue my wagon had was a lack of fuel pressure. In the process of buying the fuel pump I also purchased an AcDelco sending unit assembly not knowing the wagon had a specific one for it. The one I purchased was a sedan AcDelco sending unit which has an excellent quality and was packaged impressively as picture above. Once I notice my mistake I ordered an AcDelco and Spectra assembly and right off the bat noticed a big difference in quality. Unfortunately I do not have pictures of a side by side comparison but can tell you the following. The Spectra unit has smaller gauge wires, the bends in the tubing have noticeable flattening and the fuel gauge construction seemed cheaper. The AcDelco was a much better quality all around, the only difference being the AcDelco sedan assembly has a better finish and logo etching. Below is the side by side comparison between the sedan and wagon version.




I proceeded to lower the tank and replace the unit as well as the regulator and fuel filter. And there is where I ran into problems. When I removed the filter I noticed a little Teflon ring came out with the filter on the outlet nipple.




I thought it was odd but proceeded to finish assembly and test the fuel system. Well as soon as I primed the fuel system, fuel poured out of the outlet side of the fuel filter. I took it apart and looked inside the quick disconnect fitting and found the O-rings were missing.



So I purchased some quick disconnect fuel fittings the same size as the oem one and took one apart for the O-rings. This was the order in which they go. Notice the white Teflon ring separator, this was what was left of the original stack. God only knows how this happened. Keep in mind my father in law drove the wagon to my house about 45 minutes and it never leaked fuel. I think the low pressure was right at a sweet spot where the car ran but didn't leak fuel or at least a notable amount.




I went ahead and put everything back together and primed the system with no leaks. I cranked and started the wagon and she started right up with perfect fuel pressure. Now with that taken care of I can proceed to fix the other items.

Nice work so far!

Interesting work though. It looks really impressive.