97 flt codes P0171 & P0140 w/ 30 psi fuel pressure

[cnatsu1]

Hey guys, looking for some expert advice before I go throwing any more money at this beast. I've only got 30 psi with the car running, only had 20 with the key in the 'on' position. Picked up a fuel pressure regulator from the local jy and still have 30 psi and throwing P0171 and P0140 flt codes. I'm thinking that I need a new fuel pump. My gas gauge has never worked, so getting that working would be a positive step forward. I'm guessing the low psi would cause the lean fuel fault code. My next guess would be a faulty injector.

A little history - I've checked and rechecked for vacuum leaks, just sprayed around again today and checked hoses. I replaced the upper intake last year along with the crappy little plastic coolant elbow that cracks and breaks.

Let me know what you think. Thanks.

[J Wikoff]

Maybe it's a really clogged filter, but it's probably the pump.

[cnatsu1]

sorry forgot to mention that I changed the fuel filter last year too.

[Zazou]

You need a fuel pump. And get the Delphi.

Three weeks ago, my 98 SE started lagging at start, throwing the same codes, and refusing to start for 15+ min after running. We spent a week changing the intake, FPR, spark plugs and wires, coil swap, PCV valve and sensor, and even the battery, and finally the fuel pump. I had recently put a newer engine in a few months ago, so I had all the parts except the battery and fuel pump. I run a shop, so all it cost us was some pride. It threw us for a loop because most of the time, a fuel pump just gives up. These tend to grow weak. Very soon your fuel pressure will drop even more. Because I have that kind of luck with this car, I had to put a second pump in due to a rare defective unit from Delphi. After the second pump, fuel pressure is back, acceleration is back, even the AC blows a bit colder.

No guessing needed, you need a fuel pump.

[cnatsu1]

Thanks for the feedback!! One more question - since my gas gauge isn't working should I order a complete assembly or just the pump. Not sure what the problem might be since the gas gauge has never worked since I owned the car.

RockAuto has the Delphi pump only for 66.76 and a Spectra assy for 122.79, they also have an economy Fineline assy for 79.79.

[Bob Dillon]

RockAuto has the Delphi pump only for 66.76 and a Spectra assy for 122.79, they also have an economy Fineline assy for 79.79.

The cheapie fuel sender worked fine in my previous ride for 3 years before the car gave up it's life so other Bonnevilles might live.

If you change the pump yourself, do yourself a favor and buy the factory 0-ring with three prongs that extend down into the tank.They're about $8 at the stealership. Pumps all come with just a plain 0-ring, and it's a PITA to get that to seal. I guarantee you'll save yourself $8 worth of time and frustration.

[cnatsu1]

So here's something to make you smile. I relieved the fuel pressure when I was checking my fuel pressure regulator the first time, took out the clip, and turned around to get something and pop, bang, booey, it shot out hit the hood of the car and I couldn't find the larger o-ring. Got the air compressor and blew out everything and still nothing. So lesson learned - on a warm engine just because you've relieved the fuel pressure doesn't mean you won't still get enough expanded gas/air pressure to shoot out the fuel pressure regulator. Just saw another post on removing the fuel pump relay and turning over the car to relieve the pressure. Sounds like a better program than soaking it into a rag.

Did some searching and I guess I'm leaning towards buying the complete fuel pump assy. Anyone have any experience with the Spectra on RockAuto??

[Wes]

Spectra pumps are crap. They have a very high fail rate.

I put their sending unit, with a delphi pump in my Mom's Astro van, and it ran for years. Probably 6 or so before she got rid of it.

[Zazou]

Get whatever sending unit fits your budget, just make sure you get the Delphi pump.

[human]

I'm with everyone else. I just went through the same thing with my '97 LSS earlier this summer. The weird thing is the gas mileage went to crap after I replaced the pump. I used to get 19 or 20 MPG around town, now I'm lucky if I get 16 or 17.

[cnatsu1]

Hope my fuel mileage doesn't drop too. I just ordered a spectra sending unit from Advance auto with a $50 off $125 coupon (DOW36) that expires today. Yes, I'm a cheap bastage. A buddy has a contact that is getting me an gm fuel pump for $65 but their sending unit was $200 plus... I'll get the factory gasket from him too as someone else suggested. Hopefully will have all the parts and get this in next weekend. I'll let you know how it goes and if it fixes my problem.

[Bob Dillon]

Hopefully will have all the parts and get this in next weekend. I'll let you know how it goes and if it fixes my problem.

Run the tank down as low as you dare before the swap. It's a lot easier almost empty.

[cnatsu1]

Been a while, wife kept putting gas in the car... Changed out the fuel pump yesterday and no more p0171 faults. Fuel pressure is 35 with key on and car running. Hope my mpg doesn't tank.

Never looked for a write up on changing the fuel pump. I pulled both rear tires and loosened up the emerg brake cable to give the tank room to drop (blocked the tires). The worst part was getting the fuel lines disconnected. The first one came right off when I squeezed the two plastic clips on the end. The other two fought me. Finally got them off using my bent nose needle nose pliers (amazingly, these little pliers come in handy on a lot of projects). Disconnected the fill and breather hoses. Used a big flat head screwdriver between the tank and hose to get them started (kind of a battle, tried twisting them first with no luck). Took off the two tank straps and pulled the tank.

Grabbed my new fuel pump and sender and started test fitting parts together and the new fuel sock that came with the sender just didn't seem right. Google was my friend and I found a different style fuel sock for the new gm fuel pump. A trip to NAPA and $20 later everything is looking good.

My other battle was one of the new electrical connectors didn't want to take my old plug and I had to bend the pins in the new clip so they aligned better. Easier said than done when the tank is in and the clip is up at the top of the tank. That's what I get for buying a cheapo sending unit.

Never could get the fill and breather hose all the way back on. I pushed and twisted and got them all but the last quarter inch. There's plenty of tube inside the hose and I got the hose clamps back on tight, so it shouldn't be a problem.

But everything works and my fuel gauge works now too.

[J Wikoff]

35 is still low.

[cnatsu1]

most likely the crappy harbor freight pressure gauge.

[Bob Dillon]

most likely the crappy harbor freight pressure gauge.

Mine works fine. Hook it up again and pull off the line for the fuel pressure regulator. It should jump 10-12 psi. If it doesn't, fpr may be bad.

[cnatsu1]

didn't jump 10-15, but went up to 40 with key on and 43 with engine running. In any event, I'm not concerned as long as it is no longer throwing codes and I can get thru emissions next time. Need to get some mileage out of the new tires. I do have a spare fpr I pulled from the junk yard, just in case.

I used to be able to see my o2 sensor drop below 0 and it would throw a code. That is no longer happening, so it had to be the fuel pump and low fuel pressure.

[J Wikoff]

Junkyard FPR's should stay in the junkyard.