97 Blazer fuel pump issues

[tamerack]

Hello. I am trying to sort out a 97 Blazer for a relative. The engine was just replaced with a used unit. Since then it has developed fuel problems. It won't start without priming. Last week it died on the road and wouldn't restart. The instrument cluster was dead also. I towed it home and started looking for the ignition switch. I worked at a GM dealership until 95 but haven't kept up with the changes. The switch looked unfamiliar to me so I did some searching and found this forum. Apparently ignition switch and fuel pump problems are common on these blazers. I replaced the ignition switch with a NAPA part. Put the column all back together. Replaced the fuel filter. Electrical all functiioning but still won't start. Had to buy a fuel pressure tester to go further. Key on pressure is 45 and bleeds down immediately. After priming the engine starts , idle pressure is 52. The owner replaced the pressure regulator with the used one from the old engine. I am trying to troubleshoot this to avoid replacing expensive parts. I think my next step should be to check deadhead pressure at the fuel filter? Another symptom is the fuel gauge floats around.Possible ground problem?

[blazee]

Sounds like you are on the right track. I would do as you mentioned and check the pressure at the filter (hooked directly to the line, not "Teed" in). This will let you know which half of the system the problem is in. Obviously, if the pressure is fine at the filter the the problem is most likely the regulator, or leaking injectors/spider. If the pressure is low at the filter then the problem is behind that point. There are some problems in which the connector at the pump gets overheated/melts/etc and causes a poor connection there, and judging by the immediate bleed off their could be issues with the pulsator as well as. Of course the pump is always a possible cause, too.

Anyway, basically to summarize the above. It sounds like you are on the right track. Finding the problem will just take a little testing/exploration, and if you need any assistance along the way... just ask.

[b1lk1]

You need atleast 60psi key on/engine off at the engine for this truck to run right. Also should hold 55PSI+ for 3 minutes after turning the key off.

[mike2004tct]

I made a gauge to check exactly what causes ther quick leak-down (thanks to info provided by old-master)
Look at post #4 for a pic of it. Saves the hassle of replacing expensive parts.
The tool cost around $25.00 to make.
http://www.automotiveforums.com/vbul...ight=fuel+pump

[mike2004tct]

Originally Posted by tamerack

Hello. I am trying to sort out a 97 Blazer for a relative. The engine was just replaced with a used unit. Since then it has developed fuel problems. It won't start without priming. Last week it died on the road and wouldn't restart. The instrument cluster was dead also. I towed it home and started looking for the ignition switch. I worked at a GM dealership until 95 but haven't kept up with the changes. The switch looked unfamiliar to me so I did some searching and found this forum. Apparently ignition switch and fuel pump problems are common on these blazers. I replaced the ignition switch with a NAPA part. Put the column all back together. Replaced the fuel filter. Electrical all functiioning but still won't start. Had to buy a fuel pressure tester to go further. Key on pressure is 45 and bleeds down immediately. After priming the engine starts , idle pressure is 52. The owner replaced the pressure regulator with the used one from the old engine. I am trying to troubleshoot this to avoid replacing expensive parts. I think my next step should be to check deadhead pressure at the fuel filter? Another symptom is the fuel gauge floats around.Possible ground problem?

I just noticed you're in Lake Mills.

I'm about 30 miles south of there.

If you want to borrow the tool, PM me.


Also, on the fuel gauge floating around. This is another typical problem for 97s.
You may have the original fuel pump assembly in the tank, the sensor gets worn on them, thus the flopping readings.

[tamerack]

Today I checked the fuel pressure at the fuel filter outlet. It was the easiest place to tap in. Key on pressure was 45#. Pressure leaked down to 35 slowly then held at 35. 45# is lower than spec so I guess its time to drop the tank and see whats up. I may have a problem with the pressure regulator as well. I will check out the pump first. Any advice on which pump to buy? GM dealer, AC Delco, aftermarket? Thanks to all who replied. Will update when I have more.

[Rick Norwood]

Originally Posted by tamerack

Today I checked the fuel pressure at the fuel filter outlet. It was the easiest place to tap in. Key on pressure was 45#. Pressure leaked down to 35 slowly then held at 35. 45# is lower than spec so I guess its time to drop the tank and see whats up. I may have a problem with the pressure regulator as well. I will check out the pump first. Any advice on which pump to buy? GM dealer, AC Delco, aftermarket? Thanks to all who replied. Will update when I have more.

Stay away from Aftermarket especially Airtex Pumps.

See this thread. http://www.automotiveforums.com/vbul...d.php?t=927589

Even though the OEM pumps will give you sticker shock, stay with OEM or AC-Delco Delphi.

[blazee]

Did you connect directly to the line or use a "T". If you used a "T" then basically what you did wasn't any different than reading pressure at the schrader valve. If you connected it directly to the end of the line then I'd agree to go ahead and check out around the pump. Before actually dropping the tank, I'd check the electrical connections and voltage at the pump to make sure they were good. As for the brand of pump, AC Delco has proven more reliable, so that's definitely what I recommend.... unless you like changing fuel pumps. When changing the pump, you'll still want to check out that connector and replace it if it is bad, and of course replace the fuel filter as well.

[tamerack]

Repair update. Ordered a Delphi fuel pump from an online vendor. $270. Meanwhile dropped the fuel tank. Broke the vent valve at front of the tank, not expecting it to be there. $19 mistake. Wire connecters at fuel pump look good no melting no corrosion. The black 3 wire device must be a pressure sensor? Removed pump module. Tank looks good inside. Tested the level sender with an ohmmeter and verified it was bad. Installed new module. Installed new vent valve. Gave tank a layer of undercoating. Put it all back together. Put some gas in the tank. Bled the air out at the fuel filter outlet. Did the deadhead pressure test again. Now has 65# at key on, before had 45#. Hooked up fuel filter. Checked pressure at manifold fitting. Key on pressure 55#, but pressure still bleeds off right away.Tried to start, wouldn't fire up. Gave it a priming shot, started up. Fuel pressure at idle 55#. Before was 45#. Let it warm up. Checked for leaks. Drove it around the driveway. Didn't die like before. Took it down the road and back, ran ok. Gave it a hispeed road test, no sign of fuel starvation, no ce light, fuel gauge works now. Drove home , shut it off, tried to restart, no go. Disappointing but not unexpected. There is still a problem with the pressure regulator Supposedly it is new but pressure is bleeding off somewhere. Once the engine is started it runs smooth, doesn't seem to be running rich. Just can't fire the injecters during cranking. Called it a day at this point and broke out the millers.

[mike2004tct]

The offer to borrow my gauge is still valid.
Takes less than 10 minutes to check.
This will tell you for sure if the problem is with the pump or the pressure regulator.

[tamerack]

Repair update. I had ruled out the fuel pump as the problem. That leaves the pressure regulator and injectors and plumbing. The owner had just replaced the regulator before I got involved. I removed the plenum today. I was able to get it off without removing the upper radiator hose. I removed all the injectors and the spider as a unit so I could inspect it all. Yes I broke a couple of the V retainers for the injectors but got them all out anyway. The pressure regulator was only partly seated in the housing and the clip wasn't seated either. Apparently it wasn't leaking externally but was allowing the fuel to bypass back to tank. I can see the difficulty of trying to change it without removing the spider. You can't really see what you are doing. I am going to clean everything up good as long as it is apart . Maybe will take some pictures if I can . Does anyone know if you can replace the retainer clips on the injectors? I have another complete set but would like to use these injectors as they seem to all work ok. Anyway, I think the end is in sight for this ordeal.

[tamerack]

Repair update. OK I found the pressure regulator was not seated in the injector body. I removed the fuel spider from the engine . I cleaned the carbon from the injector tips with gumsolve and a safety pin. I installed the pressure regulator (this was a new part). I put the spider back in position so I could pressurize it and check for leaks. Hooked up fuel lines and ran pump from test lead connecter. Had 62# with pump running. Pump off, pressure bled off right away. No sign of external leakage. This didn't seem right. Now what? The regulator is new. I looked it over. It has a part # but doesn't look like oem. I also had a used one that had come out of one of the engines. This one looked original, it had an adjustment screw with a tamperproof torx . Up to this point, I didn't understand the purpose of the vacuum port on the pressure regulator, since it didn't connect to anything. After thinking about it I realized that with the plenum installed and the engine running there would be manifold vacuum inside and the regulator would be sensing manifold vacuum. OK, why not check the regulator with a vacuum pump. I hooked up my mityvac. The regulator held vacuum. I tested the used regulator. It also held vacuum. I decided to try the used regulator. Hooked it up, pressurized the system. Had 62# with pump running, but held some pressure with pump off.I could get it up to 50# and it would slowly bleed down. This was an improvement. It seems the new regulator was defective or it got damaged somewhere in the process. I decided to go with the used regulator . Another point. I had no fuel spray from the injectors when I keyed on the system. I figured I needed a cranking signal before the injectors would spray. At this point I wondered if I could test the pressure regulator with the vacuum pump. I hooked up the fuel lines, pulled a vacuum on the regulator, and ran the pump. Now I had 55#. When I released the vacuum, pressure went up to 62# This makes sense to me. The regulator responds to engine load. I decided to try this setup. I snapped the injectors in place and installed the plenum. It went pretty well.I lubed the opening around the injector body with liquid soap so the oring wouldn't roll. I had to pull the body up slightly into the plenum. Hooked everything up. Checked pressure again. 62 at key on. Cranked it, it runs. Finally. Has 55# at idle. Rev it and pressure goes up. Basically ranges between 55 and 62. At this time the vehicle is running and starting ok. To be continued...