Fuel pump dying or another problem?
 

My BLM's and INT's were all staying between 126-131 in all ranges and power levels, all of a sudden they were at 137 in all ranges, etc. while I was headed to the car show at Pismo this weekend. So I changed injector sizes in the PROMinator and it ran great, albeit a little rich (124 BLM) still got 24 mpg though. On the way back it started running really rich so I changed back to the original bin and everything was back to 128.

Yesterday morning, the car fired up at the first blip of the key. I drove about 7 miles and stopped at a convenience store. I came out, the car coughed at the first blip of the key and that was it. I ran the battery dead trying to start it with no success. 20 minutes later a friend I called showed up with some jumper cables (both sets I own are on the garage floor... duh!). Car started on the first try.

Since I was now running extremely late for work I got on a back road and let her rip. At 4800-5000 rpm in third she started hacking. I backed off and hit it again with the same result. The third time she pulled hard all the way up to 5500 in third and 4500 in fourth when the kick down kept me from going any higher.

Since I used all my gas heading to work, I went to a small town close to where I work to get some more. The car fired up at the first blip of the key. Drove 6 miles, got gas and the car wouldn’t start. It coughed on the first blip of the throttle and then no more. After the third attempt to start the car I decided to play with the pedal like you would with a carb. The car started coughing like it was trying to start, but to no avail. Again, I ran the battery dead....... A few minutes later, I got a jump and the car started fine. (The car was turning over fine till I ran the battery dead.)

So what do you guys think? The BLM’s were normally a little off at idle (137) and a little rich at 2250 (124) so I know I need to tweak those, but the car has run great for years with these same basic settings, and for a month with these same exact settings. Oops, it did this to me once last week which I thought was an aberration, but it was the same thing. Cold car, short trip, won’t start.... with normally ½ tank or better. It was only ¼ the last time.

TPS ?
 

Sounds to me like a TPS issue. Could be flaky output causing no fuel (if over threshold for flood clear)
Do logs show any jumping of the output?

How does your charging system look? 13.7 volts most of the time or less than that?

Re: Fuel pump dying or another problem?
 

How many miles are on the pump?.
I change mine at least ever 3rd year.

Charging system looks good. Even at idle with the stereo maxed, AC/ on high, and high beams on I'm still over 12 at the battery. With the stereo normal and low beams on it's over 13. I think when it's time for replacement I may have it built to a 120 amp unit. The car has been like this for 10 years so I'm not thinking that is the problem.

The TPS is the original with 190,000 miles on it but it signals smoothly throughout the range with a digital volt/ohm meter attached. I am thinking about getting a spare because I know that it has to be getting close to the end of it's life.

The pump has about 100K on it and the symptoms seem like a fuel pump going out, but I've only had mechanical pumps for carbs go out on me. Other people I know have had electric pumps go out and they mention that they just quit with no warning, however, they are not car people, and car people notice things that regular people don't....

What size fuel pump would you guys recommend for what I have for an engine???

If the stocker lasted this long, not a bad choice I'd say. I use a Walbro 307 in my GN, many use the Walbro 340, also popular in Corvettes I believe.

Yeah, probably pump or relay, but make sure it isn't ignition.

The pump is a Buick GN pump that I put in at 90K. I just hit 190K (on the body only) heading to Pismo for the car show. I recently changed from 24# injectors to 30# injectors and my top end improved considerably. A lot of that could be getting my fuel curves leaned out as they have always been rich, even before the injector swap.

The only electrical thing that hasn't been replaced on the whole car is the reluctor(?) in the distributor. All of the modules have been replaced and the 53K volt Hypertec coil has maybe 15K on it. The plugs, wires, distributor cap and rotor have 6K on them. The O2 sensor has about 1000 miles on it. I'm getting ready to swap it out for an AC/Delco 3 wire unit in the near future...

Does anyone know the output of the stock GN pump? I figure I can get the Walbro information from them. I have a new fuel pump from TPIS that supports 550hp but I have concerns that it may be too bug for my application and the return line not be able to handle it. Have any of you guys used that Bosch (TPIS part# 300-178) "in tank" unit?

Thanks for the help guys!!!!!

:thumbsup:

Check here:

http://www.gnttype.org/techarea/fuelsystem/pmprate.html

A wealth of information in other areas of the tech section at gnttype.org too.

Mark

I'd replace the pump but it doesn't explain the no start issues. Sounds like a charging problem to me.
To find out if it's the pump, hookup a fuel pressure gauge and look at it. When your injector DC goes up to like 75% and then sum, how's the pressure holding up? 3rd gear does good for testing the pressure dropping. When the injectors are open, and if the pump can't keep up with the volume of fuel being consumed, the pressure drops off noticably.

Yep, it's time to tape a F/P gauge on the windshield and drive around. Go WOT and count to 5. The fuel pump might be bad if fuel pressure drops within that time. I still would check the regulator and BOTH fuel filters before really considering the fuel pump.

I definitely need to do the pressure test and I do have a fairly long hose on my pressure gauge. I did go to the GN site to get the figures on the stock GN pump. The Walbro 340 looks really good and should fit in the stock holder in the tank. The Bosch unit I have is not going to fit in the stock hanger as it is about 50% larger diameter and about an inch and a half longer.

I need to write down the Bosch part number to see its actual ratings. The Walbro 307 and 340 were both rated at a higher horsepower figure than the Bosch unit and look to fit in the factory hangar. The only difference I could see between the 307 and 340, was the 307 was a high pressure unit.

As far as the electrical goes, the engine turns over fine and for a long time before it runs down. The fuel filter has about 1500 miles on it and the regulator has the same....... The jam nut on the adjustment bolt was still tight as well. Where is a second filter in the system on an 85 Camaro? You have a screen on the pump, screens in the injectors, but only one actual fuel filter....

My BLM's were running 147 at Idle and I made a small change to the MAF table and got it to 137. Since it started fine at 147, albeit idled with a lean miss, it should start even better at 137. I fully intend to make another change to get it to 128, but I need to figure this thing out first.... Unfortunately, I didn't have time to work on it this weekend... I'm way too busy!!!!

I changed my Original FP last weekend, and the symptoms sound awfully familiar. What you may have is a dead spot in the FP motor. When you shut the car off it has a 1 in 4 (number out of my butt) of landing on a bad section, but every time you try to start the car it will twitch a little, after a while it makes it to the next good segment.

My problems were a little different, as every now and then I would get this horrible stumbling when I tried to start the car. Hit the gas, it would stall. Then I would open the hood, shake my head, and try to start it again and it would start fine. It did this for a year and about 1000 miles. The FP finally gave up and it would fire and die, Fire and die instantly. Then I rememberd I could hear my FP when I turn the key.... Not any more...

How to:
-- Jack car up as HIGH as you can, put Jackstands just in front of leading control arm. The higher the better you will see why.
-- Remove Wheels
-- Get bucket, remove Brake line on LH side, let drain into bucket.
-- Remove pan-hard bar,
-- Disconnect sway bar Both sides
-- Remove Driveshaft and torque arm
-- Place jack under axel and raise slightly to remove the lower shock nuts and bolts.
NOTE: I did NOT need to remove the control arms, although I did, it would have been easier ro re-assemble if I did not however.
-- Drop Axel, and catch springs as they are rolling away from you at this point.
-- Disconnect 2 7mm screws from cross frame connector.
-- Remove rear cross frame connector (above pan-hard bar)
-- drop Exhaust (if you are able to disconnect it so its out of your way, mine had a U-Bolt over the axel that would have made it easy to do but the exhaust had a crimp in it from the bolt being really tight so it was not possible.
-- Remove both shields
-- Get red gas tank, Get something you can prop it up with, like a bucket, some wood, whatever you think you need.
NOTE: There are 3 Fuel line tubes, one (3/8") should have a compression type fitting that is unscrewed, 1 is 5/16" and the other is 3/16" or 1/4" The 3/8" is Supply, the 5/16" is return and the smallest one is for emissions.
-- Remove the 5/16" one first, and let the tank syphon into the Red Gas tank
-- Remove the other two hoses. and the Fuel Tank breather.
-- ON THE FENDER Remove The filler door, the inner trim piece and the Fuel cap.
-- remove 2 forward 15mm bolts from the fuel tank straps, and drop Fuel tank
-- Clean fuel tank top so not to contaminate Fuel.
-- Using a hammer and a screwdriver gently work the sheet metal clip counter clockwise. NOTE: You will only go so far before you have to change your tapping point.
-- Replace FP as per instructions
NOW you have to put it all back together. Just reverse process.

Enjoy. Get a Fire extinguisher, and have fun ;)

One thing I thought was curious was just before my FP finally went, my BLM's droped to 105... I am still scratchimg my head on that one.

John

Since it just turned hot here, I'd be suspicious of the reluctor too.Walbro pump source

My bet is on fuel pump. I've had fuel pumps go out on me on the street a couple of times and they don't always "just quit". I had one that had me fooled for a while....The vehicle would run fine unless you had 1/2 tank or less of fuel and had been driving for 20 minutes. It would start hesitating and missing etc, ect...Fill er up with gas, problem went away. Thought it was bad gas, until it did it again, and again. The symptoms worsened until I finally changed the pump (after hunting through a lot of other stuff first).

Another time, in another vehicle (when I was smarted and started datalogging :D ) I had a pump start to crap out on me. Same symptom except it wasn't missing yet. I could see my BLM's slowly rise until I got a lean O2 code. Fill er up w/ gas & everything was back to normal.

The heat built up in an in tank fuel pump rises a lot below 1/2 tank and sky rockets when the level gets below 1/4 tank. When the pump gets hot, it craps out. ( I did a heat transfer analysis on it in college.)

Point is, it's not worth getting stranded. I'd say you got your money's worth out of that fuel pump with 100K on it. I'd change the pump and even if that's not it, it's one less thing to worry bout.

-M

I got lucky, mine died in my driveway at my Garage door... I turned off the car to unlock the garage door, went back to start the car... nothing... Had to push it in the garage. :D

John

Finally I get a chance to reply.... Waaaay too busy!!!!!

I just ordered a Walbro 307, which as it turns out is the low pressure unit, the 340 is the high pressure unit. They say the 307 will actually outflow the 340 at 43# but at 60# and above the 340 flows higher. I'm also going to replace the fuel pump relay while I'm at it.

This happened before it hit triple digits here in Bakerspatch, but replacing the reluctor is a good idea. Might as well do that while I'm at it.

Thanks for all the input guys!!!!!

I had a fuel pump problem a couple of years ago. Sometimes no start, other times it was fine. When it wouldn't start I had to reach under and bang on the gas tank a couple of times. I've seen other cars do the same thing. But it ran fine after it started. Bad electrical connector can do that too. That many miles on a pump is enough. I would change it and check all connectors.

Poor lil TBI pump couldn't keep up.:eek:

You're the first person I know of on this board that has caught that....... I don't think it's common knowledge that the Buick GN pump, while used with multiport injection on the GN, is actually a TBI pump. That's why it was a third of the cost of a new Camaro TPI pump back 10-11 years ago.

:thumbsup:

I think the reason why they did not need the extra pressure on the GN was they used SFI instead of batch fire. Instead of firing twice they only fired once. Also they used larger injectors Where ours are 19# & 22# from the factory for TPI, the GN & GNX I think is up in the upper 30# range.

Grumpy would know more on this, but if memory serves...

John

I think the GN's actually they run the same fuel pressure as our cars (IIRC). The injectors are 26# units. The most common things guys are installing is 36# injectors, Walbro GSS340 fuel pumps and larger turbines from what little I've read on their site. There are of course some guys building really nasty stuff as well.....

Anyways, I did finally catch the fuel pump not coming on at all. The gas tank will get dropped tonight as the Walbro 307 came in the mail yesterday. The fuel pump relay is on order and will get here today or tomorrow.

The guy at Three Way Chevrolet (original site) said that my car didn't come with a fuel pump relay, The guy at Three Way Chevrolet (New Site) said the same thing. I gave him the number off the relay I bought from the old location 10 years ago and asked him what it was...... he said it was a fuel pump relay..... DUH! Needless to say I had him order me one. Hope to have the car back on the road this weekend.....

Does anyone know the location for a fuel pump relay on a 83 crossfire trans am?thanks
Im gonna change my fuel pump but id like to change the relay 1st and see if that helps

Just aguess, but I think the Electric fuel pumps were all in the Tank...

John

I know that ,but wheres the relay?

I believe it on the firewall in the engine bay by the Brake Booster... Which one I do not know... I oinly have the Schematics for Port FI GM systems...

Sorry. I misread your post.