Did BUICK Actually Do this???

[TurboGeezer]

Helped a friend put in a Walbro pump a few weeks ago. Now the TR runs rich no matter what we do. Traced the problem to possible high fuel pressure......he is using a "237".

We noticed with the engine off that the pump would spike to 50lbs while it was on and then drop to 43lbs with the pump off.

With the engine running, the FP stayed at 50lbs, vacuum off and dropped to 44 with the vacuum plugged in.

It seemed that the regulator was doing everything that it could, but that there was a restriction in the return line that would not allow the regulator to drop to 43lbs whenever the pump was running. Therefore, we started tracing lines in order to find a clog or kink or something. We found NOTHING. However, we did manage to find that the SMALLEST of the three lines going into the tank was the return line (the medium was the vent and the largest was the feed. This is how they trace out all the way to the front of the car.

I CAN'T BELIEVE THIS!! IS THE SMALLEST LINE REALLY THE RETURN??? DID BUICK REALLY PLAN IT THIS WAY???

I do not see any other way that these lines could be hooked up at the front of the car. Besides, he bought this car at a 15,000 mile original car. NOTHING has been changed on it. However, the return line is definitely THE SMALL ONE!!!

I believe that the pump is creating far too much volume for that little line and this is why our FPR is unable to regulate the fuel properly.

ANY IDEAS?????????

TG

 

[Geoff87]

Before doing anything else...

Verify that the FP Gauge is reading correctly, by swapping it with another. It may just be a bad FP gauge.

Mine was reading 10 lbs over what the FP actually was. I only realized that the FP gauge was bad AFTER I did the 340 FP & hotwire swap. A lot of wasted time and effort on my part, in trying to figure out the problem.

 

[TurboGeezer]

FP Gauge

Thanks. I did check the gauge against a known good, very accurate gauge. They both read within 1/2 psi of each other.

I unhooked the SMALL return line back at the tank and ran the pump. I still get the same 50psi with the pump running. Therefore, I do know that my problem is not in the sending unit, etc....................thank goodness I dont have to completely drop that again, especially now that it is full of fuel.

I'll keep searching for a kink or something, but I have yet to see anything and I have traced the line three time now. I am also going to blow some compressed air through the line now that it is unhooked from the tank.

WILL A HOTWIRED WALBRO OVERCOME THE SMALL 1/4" LINE???

TG

 

[MSDGN]

Bad Regulator?

 

[325DR]

Put an adjustable fuel pressure regulator on the car and turn it down. The 237 is not adjustable. Thats all there is to it.

 

[86gn]

One of the old tricks people used to do was smash the top of the stock regulator down to give it more pressure.Someone before you might have done this, I agree with AintGoinSlo get a good adjustable regulator.

 

[TurboGeezer]

Not the Regulator

Thanks for the suggestions guys, but its not the regulator. I tested it on the bench with a spare pump and it regulates to 43psi fine. We also replaced it with a known good 233 regulator. With the 233 in place, the pressure jumps up close to the same 50psi and then settles back to about 35psi once the pump is off.

I'm pretty sure its a restriction somewhere in the return line. I just have not found it yet............unless it is the line itself

TG

 

[tim87tr]

FP Problem Diagnostics

 

[Low Budget]

WILL A HOTWIRED WALBRO OVERCOME THE SMALL 1/4" LINE???

I have no direct experiance with this problem myself, but I could swear I've seen this before on this site. Did you do a search on return lines perhaps?

I'm pretty sure the answer to your question is yes as I remember it.

Jeff

 

[salvageV6]

Mine was at 70psi. for a while one winter. What fun.

Anyway mine was blocked at the point where it goes from 3/8 to 1/4.

Point is a juntion of two hoses directly under the power steering box.

Follow the lines you can't miss it.

I used a steel wire to clean out the obstruction.

You might be able to try a hose into a can from there and see if it regulates properly with the can being your return line termination for the test.

 

[burnout]

Did you hose clamp the rubber line that repalced the pulsator?

 

[Geoff87]

Originally posted by salvageV6
Mine was at 70psi. for a while one winter. What fun.

Anyway mine was blocked at the point where it goes from 3/8 to 1/4.

Point is a juntion of two hoses directly under the power steering box.

Follow the lines you can't miss it.

I used a steel wire to clean out the obstruction.

You might be able to try a hose into a can from there and see if it regulates properly with the can being your return line termination for the test.

I remember that!.. I think you referred to the blockage as "frozen smegma".

 

[salvageV6]

Yup, didn't want to scare the guy from doing the job, I think it would be much worse looking in the summer.

 

[GNVAIR]

I had the same problem with mine in the middle of the winter.
Fuel pressure would peg itself at 50+ lbs and wouldnt budge no matter what. Tried 3 different regulators with no change. I ended up removing the regulator and the rubber line back at the tank and blowing 100+ psi of compressed air into the return line. I did it from the front and then from the back making sure that the line was clear. I reassembled and my fuel pressure miraculously returned to where it was supposed to be. Yes, the return lines are pretty jerked off on these cars.

 

[TurboGeezer]

In-Line CRUD

Thanks guys. Yeah, I think that we will find some CRUD somewhere in the return line. I certainly cannot find any kinks in the line. With only 15k miles on this car, it has not been driven much. This usually tends to let CRUD and stuff build up in wierd places.

I did research these archives and the gnttype archives before posting here..........lots of great information, but the jury is still out on being able to "overcome" the stock return line. I remember TurboDave saying that he had no problems, even with a Double-Pumper setup.....both pumps running.

I just cannot believe that GM used a little 1/4" line for the return of a NON-compressible fluid and used a comparitively larger line just for the vent. Actually, a friend once worked for Delco and always lamented the fact that GM would compromise and marginalize at the drop of a hat just to save 2 cents. I guess the 1/4" line is cheaper.............besides, who would ever want more performance from one of these cars, anyway

Burnout, I am curious about the "pulsator" question. What were you getting at exactly??? We did replace the pulsator. However, with all of the aftermath, I frankly have forgotten what we did there. Anyway, I have disconnected the line above the tank and still have the restriction. Therefore, I'm pretty sure that my problem is not in the tank..........thank goodness!!!

TG

 

[azgn]

the return line is easily overcome with a double pumper at less than WOT....that is why the second pump comes on only at some boost level approaching WOT

if I turn on the second pump at idle, my fuel pressure goes to 60 lbs.......

 

[TurboGeezer]

May have Found it

I may have found the restriction.................Not only is the return line so small, but I also cracked open the connection where the line turns from 5/16" down to the 1/4" size.............WOW!!! It is even SMALLER right there at the connection.

GM nipples down the line right at the connection so that they can use an o-ring seal. The passageway that is left for the fuel is not even 1/8" big. I'll bet the hole size is only about 0.090, if that.

Well, it may be time to get out the drill or something...........

TG

 

[TurboGeezer]

Increase your FLOW area by 100% in just 15 mins.

As a follow-up to an original post (see below):

The return line on a stock GN "nipples down" to 2.5mm dia. at the connection (under the front of the engine) where the line changes from 5/16" to 1/4". Therefore, the actual passageway is only 1/10" (2.5mm) at this junction. This was giving us problems with the new Hotwired Walbro. However, in just 15 minutes time you can increase this area by 100% !!!!

Just start with a 7/64" drill bit in a dremel tool (can't get a drill into the cramped area under the engine front) and progress then to a 1/8" drill and then finally to a 9/64" drill. This will open up the passageway by 100% in area (0.0158 in sq vs 0.0079 in sq) and still leave plenty of material at the nipple to hold the sealing o-ring.

This solved our high fuel pressure problem and now the 237 regulator gives 45psi, vacuum off and gives 38psi, vacuum on, at idle. Before, we could not get the regulator to go below 50psi.

NOW we're flow'n some fuel !!!!!!!!!

I was a little harsh on GM for doing this However, with the stock setup, perhaps they intended this restriction so that if the FPR failed, you could still maintain enough pressure to inject fuel into the engine. I don't know.........just a guess.

Originally posted by TurboGeezer
Helped a friend put in a Walbro pump a few weeks ago. Now the TR runs rich no matter what we do. Traced the problem to possible high fuel pressure......he is using a "237".

We noticed with the engine off that the pump would spike to 50lbs while it was on and then drop to 43lbs with the pump off.

With the engine running, the FP stayed at 50lbs, vacuum off and dropped to 44 with the vacuum plugged in.

It seemed that the regulator was doing everything that it could, but that there was a restriction in the return line that would not allow the regulator to drop to 43lbs whenever the pump was running. Therefore, we started tracing lines in order to find a clog or kink or something. We found NOTHING. However, we did manage to find that the SMALLEST of the three lines going into the tank was the return line (the medium was the vent and the largest was the feed. This is how they trace out all the way to the front of the car.

I CAN'T BELIEVE THIS!! IS THE SMALLEST LINE REALLY THE RETURN??? DID BUICK REALLY PLAN IT THIS WAY???

I do not see any other way that these lines could be hooked up at the front of the car. Besides, he bought this car at a 15,000 mile original car. NOTHING has been changed on it. However, the return line is definitely THE SMALL ONE!!!

I believe that the pump is creating far too much volume for that little line and this is why our FPR is unable to regulate the fuel properly.

ANY IDEAS?????????

TG

 

[Low Budget]

Wyle Coyote: Super Genius!!

Congratulations on solving your problem.

I believe the answer "was" yes. The return line "can" be overcome.

I'll keep this in mind for myself as I step up fuel delivery in the future.

Thanks. Jeff

 

[TurboGeezer]

Hope this HELPS

Thanks Jeff,

I hope that when the next person does an archive search that this thread will help with possible return line questions.

TG