Gain extra benefits by becoming a Supporting Member Click here find out how!
Classic Performance Products Classic Parts
Ciadella InteriorsAmerican Auto Wire Classic Industries
Chevs of the 40sDanchuk Catalog
Hellwig Products IncPerformance Rod & CustomEcklers AutoMotive
Nu-Relics Power WindowsRain Gear Wiper Systems
Impala Bob's Bob's Chevy Trucks Bob's Chevelle Parts Bob's Classic Chevy



Username Post: AC Delco fuel pumps gone bad twice now        (Topic#352876)
sgian 
Valued Contributor
Posts: 4573
sgian
Loc: MO
Reg: 12-25-03
09-06-18 12:21 PM - Post#2745494    

Have AC Delco fuel pumps gone down in quality? Besides for low fuel tanks, bad gas, electrical problems, or moisture in the tank (none of which I believe apply), is there anything else that can make fuel pumps go bad about every 2,000 miles?

I bought a 99 Suburban (old style) with a 5.7 in February of this year, it was not running due to a bad starter and fuel pump. I put a new AC Delco fuel pump in right away, at about 219,000 miles. I also replaced the electrical connector and the fuel filter. Everything was fine and it ran great with about 20 mpg highway.

Then in May I began having hard start problems. I would have to leave the key on for a few seconds to prime the fuel system before it would start. So I put a fuel pressure gauge on it and found that it was losing pressure once the fuel pump turned off. So I replaced the regulator, and that didn't fix the problem. Then I warrantied the fuel pump and got the same model AC Delco fuel pump. The connector looked good but I don't remember if I replaced it too or not. That was at about 221,000 miles, and then it no longer lost fuel pressure and it started right up again. Even though fuel pressure was about 52 psi at idle and almost 60 psi when revving the engine, the Suburban ran well. I even took it to a mechanic because I thought maybe my fuel pressure gauge was bad, but he got the same readings and said it was fine since it went over 55 psi when being revved.

So now it is having a different fuel problem. It still runs great, but is getting the SES light and the 171/174 codes. The first SES light was last week at about 223,200 miles, so I found the pressure was at 49 psi but would go up to about 58 psi when revved. Over the weekend I replaced the fuel filter and tested the electrical at the fuel pump (after dropping the tank of course). It was only a 0.4 volt drop at the connector from the battery, so my understanding is that the electrical is ok. Then I put it back together, cleared the codes, and it got driven the past few days.

Today the SES light came back on with the same lean engine codes. Fuel pressure is still about 49 psi at idle, and about 56 to 58 psi at rev. The fuel gauge rarely ever goes below 1/4 tank (it only has gone under 1/4 tank a couple times I think, when my wife drove it). I don't use the cheapest local fuel brands, just mostly BP and Murphy. And no fuses are getting blown, and the voltage drop is 0.4 volts. So I am wondering if there is something else I need to check before replacing the fuel pump again? Or is it likely that I got two bad AC Delco pumps in a row? I am thinking of getting a Carter fuel pump next time.



 
bowtie44s 
Valued Contributor
Posts: 4032
bowtie44s
Age: 35
Loc: wv
Reg: 08-29-12
09-06-18 12:25 PM - Post#2745496    
    In response to sgian

I'd be looking for vacuum leaks.

Jeff

'88 Chevy K3500, aluminum head roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap


 
sgian 
Valued Contributor
Posts: 4573
sgian
Loc: MO
Reg: 12-25-03
09-06-18 01:04 PM - Post#2745499    
    In response to bowtie44s

I didn't see any disconnected or broken vacuum lines, nor did I hear a vacuum leak when I checked. I haven't sprayed the intake manifold with anything to check the gaskets though. Since it is 49 psi at idle I stopped looking for a vacuum leak and thought it was a fuel pressure problem.



 
Shepherd 
Frequent Contributor
Posts: 1418

Loc: Lake George, NY
Reg: 11-11-15
09-06-18 02:25 PM - Post#2745508    
    In response to sgian

If this is a Vortec , 60 psi is required. Also at that mileage the injectors could be contaminated. Exhaust leaks can affect o2 readings also.



 
elcamino 
Dedicated Member
Posts: 5354
elcamino
Loc: Lake Superior-Michigan US...
Reg: 03-30-00
09-13-18 09:51 AM - Post#2746038    
    In response to sgian

Friend is a former Chevy parts manager and now owns an AC Delco Service Center. He has been commenting lately that AC Delco is gone over to the cheap side. Their oil filters are junk, insides look like cheap Frams, Some of their replacement parts are made in China. They seem to have 2 quality lines, ones they sell to GM dealers and one for the aftermarket. Big price difference.

Check to see where the fuel pump is made. US or Canada are good, anywhere else

Its not so much that they don't want to sell US or Canadian made, just no manfactures left to make them here. GM has divested itself of part manf. and everything comes from the lowest bidder supplier. All manf. are the same.

Mike
2017 GMC Sierra Denali Ultimate 6.2L(420hp)/8-sp Z95
2016 Polaris RZR 900 EPS


 
454cid 
Valued Contributor
Posts: 2944

Age: 45
Loc: West Michigan
Reg: 02-18-12
09-13-18 12:19 PM - Post#2746045    
    In response to sgian

I just ordered a Denso pump through Advance Auto. I was really torn what to buy. I'm replacing a 14 year old AC Delco that was purchased through the dealer. I don't have that kind of money now. I'm not sure if the AC Delco pumps available elsewhere are different or not, but they've been redesigned. There's a new part number now.

I tried ebay for some old stock, but they were either very expensive, or a great price but sketchy looking auction listing.

Denso is another OEM supplier to many of the automakers. They are basically "Delphi" to Toyota, but separated from Toyota much earlier than Delphi did from GM.

Advance has coupon codes for online purchases, and often times if they see you're on the site, but don't order, they'll up the discount. They were actually cheaper than Rockauto for the pump when all was said and done.


99 K3500 RCLB


 
Shepherd 
Frequent Contributor
Posts: 1418

Loc: Lake George, NY
Reg: 11-11-15
09-13-18 01:47 PM - Post#2746052    
    In response to 454cid

Fresh fuel filter with this of course.



 
KoolBreeze 
Poster
Posts: 14

Reg: 07-29-18
09-13-18 03:23 PM - Post#2746068    
    In response to elcamino

  • elcamino Said:
Friend is a former Chevy parts manager and now owns an AC Delco Service Center. He has been commenting lately that AC Delco is gone over to the cheap side. Their oil filters are junk, insides look like cheap Frams, Some of their replacement parts are made in China. They seem to have 2 quality lines, ones they sell to GM dealers and one for the aftermarket. Big price difference.

Check to see where the fuel pump is made. US or Canada are good, anywhere else

Its not so much that they don't want to sell US or Canadian made, just no manfactures left to make them here. GM has divested itself of part manf. and everything comes from the lowest bidder supplier. All manf. are the same.



Sounds like the industry is going in the crapper. It may continue to go that direction until the costs associated with warranty claims and etc outweigh the savings of the cheap parts. Very sad.




 
sgian 
Valued Contributor
Posts: 4573
sgian
Loc: MO
Reg: 12-25-03
09-14-18 05:55 AM - Post#2746130    
    In response to Shepherd

So I replaced the fuel pump again, this time with an airtex. Fuel pressure is the same at idle, 49 psi warmed up with the new fuel pump. I'm thinking it isn't the fuel pump, but some obscure problem.

When the engine is off and key in the on position, fuel pressure is 59 psi. With the relay bypassed, fuel pressure is still 59 psi. So the engine only has low fuel pressure at idle. When the engine is running and the engine is revved, fuel pressure goes up then drops back down.

There is no voltage drop to the relay, and .4 Volts drop at the wire connector at the pump. So the electrical seems ok.

I've replaced the fuel pump 3 or 4 times now, and the fuel pressure regulator. I've checked for fuel leaks and vacuum leaks.

I took the gas cap off in case it is the evap vent. Still 49 psi at idle. I disconnected the lines at the canister, both to and from. Still 49 psi at idle. So I don't think it is the evap system creating suction at the tank to hold down fuel pressure while the engine is running.

*edit I forgot to mention that I don't hear any exhaust leaks. My state has safety inspections, and it legitimately passed so the inspector didn't find exhaust leaks either. The engine runs smooth and sounds good. Also the fuel filter has been replaced twice this year.

So what else is there to check?



Edited by sgian on 09-14-18 09:45 AM. Reason for edit: adding stuff

 
sgian 
Valued Contributor
Posts: 4573
sgian
Loc: MO
Reg: 12-25-03
09-14-18 09:43 AM - Post#2746141    
    In response to sgian

[img]https://www.dropbox.com/s/il02tzokysy2e4g/Pho to%20Sep%2014%2C%2010%205 7%2034%20AM%20%281%29.jpg?dl=0[/img]
I checked the spark plugs, and except for the one with ash deposits (probably burning oil in that cylinder) they look good to me. So it hasn't actually been running lean very often if at all, despite the codes. Could the MAF or oxygen sensors giving wrong readings make the computer reduce the fuel pressure? I'm not sure if that is possible, since fuel spray I thought was controlled by the injectors and not fuel pressure.



Edited by sgian on 09-14-18 08:18 PM. Reason for edit: trying to get the image to show up

 
sgian 
Valued Contributor
Posts: 4573
sgian
Loc: MO
Reg: 12-25-03
09-14-18 01:42 PM - Post#2746151    
    In response to sgian

Something that might be a coincidence, both times the SES light came on with the lean codes, it was raining outside and the A/C was on. Also the vehicle shakes at 65 mph, but I don't know if that is engine or suspension related.

I did a vacuum test today to see if I missed any vacuum leaks. The vacuum gauge showed fairly steady about 22 psi, so it seems unlikely to have a vacuum leak.



 
65_Impala 
Very Senior Member
Posts: 4070

Reg: 12-29-02
09-14-18 01:50 PM - Post#2746152    
    In response to sgian

Does the regulator have a vacuum line running to it?



 
sgian 
Valued Contributor
Posts: 4573
sgian
Loc: MO
Reg: 12-25-03
09-14-18 02:35 PM - Post#2746158    
    In response to 65_Impala

There is no vacuum line to the regulator. The fuel pressure regulator on the 5.7 vortec is inside the intake manifold, so I guess it gets vacuum directly rather than through a hose.



 
CowboyTrukr 
"7th Year" Silver Supporting Member
Posts: 4014
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
09-14-18 07:41 PM - Post#2746191    
    In response to sgian

Pretty sure 65 Impala is right on the money.
Here's the regulator. Note the hose bib on the bottom. That's where the vacuum connects



Attachment: Capture.PNG (482.74 KB) 14 View(s)

Greg

'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500
'00 Explorer XLT 4.0 V6 Auto
'94 K2500 5.7 NV4500 ECLB - SOLD
‘87 GMC S15 SCLB 4.3 Auto - SOLD

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke


 
sgian 
Valued Contributor
Posts: 4573
sgian
Loc: MO
Reg: 12-25-03
09-14-18 08:06 PM - Post#2746192    
    In response to CowboyTrukr

Thanks for looking, but look at the picture again. That is inside the intake manifold with the upper intake manifold removed. There is no vacuum hose when the entire thing is under vacuum from the intake passages surrounding it. I was confused too when I first saw what looks like a vacuum attachment inside the intake manifold when I opened it up.



 
sgian 
Valued Contributor
Posts: 4573
sgian
Loc: MO
Reg: 12-25-03
09-14-18 08:17 PM - Post#2746194    
    In response to sgian

Here is an exploded view of the 5.7 vortec intake and spider injection. Notice that the spider is inside the intake manifold when it is assembled, and that there is no vacuum hose to the regulator.




 
Tony 
Founder & Grand PoohBah
Posts: 17726
Tony
Loc: Orange County CA.
Reg: 03-15-99
09-15-18 07:23 AM - Post#2746210    
    In response to sgian

.



 
Bel Air kiwi 
"3rd Year" Silver Supporting Member
Posts: 4328
Bel Air kiwi
Loc: New Zealand
Reg: 04-24-14
09-16-18 09:35 AM - Post#2746324    
    In response to sgian

Hi Sgian, Not my specialist area, but one of the hardest things to diagnose is the breakdown of the inner lining of soft hoses. It is really hard to work out in either brakes or fuel. Short of taking a section out and splitting it you can't tell.

Since you mentioned the weather and using Ac I recalled a RHD conversion here that would run fine then jump to limp home mode. After months of searching that turned out to be a dry solder join that was effecting earthing.

Cheers Kiwi

48 3100 RHD, 51 Deluxe 4DR RHD, 51 Bel Air parts car, 52 Bel Air P-Glide LHD. Others 23T, 32 Tudor, 58 Edsel pacer 4DR HDT, 79 F250 351C RHD. 69,70,82 Capri. No mobile, no TV, and no Jap cars.

"They made a desert and called it peace." Tacitus


 
65_Impala 
Very Senior Member
Posts: 4070

Reg: 12-29-02
09-16-18 09:12 PM - Post#2746392    
    In response to sgian

  • sgian Said:
There is no vacuum line to the regulator. The fuel pressure regulator on the 5.7 vortec is inside the intake manifold, so I guess it gets vacuum directly rather than through a hose.



If the regulator has vacuum applied to the other side of the diaphragm then the pressure will vary as the vacuum varies. I believe it is around a 2:1 ratio, so with 22 in-Hg vacuum you'd see about a 11psi drop in fuel pressure. This matches your vacuum and pressure readings fairly closely.

The service manual say the pressure should be 60-66psi when running the pump engine off and 55-60psi when idling the engine. No idea if this is right or not, but it doesn't seem correct for a vacuum referenced regulator. I have seen errors in the manuals before.

It doesn't really matter if there is an actual hose or not. All that matters is if the regulator diaphragm sees engine vacuum. So quit getting your panties in a bunch over the hose.

And no, the ECM does't control the fuel pressure. The lean codes are not directly fuel pressure issues. For the code, you should also check the exhaust for leaks, the intake tract after the MAF for leaks, the AIR system for leaks and that the PVC valve is correct for the engine.

You can also run an injector balance test to see if an injector appears to be bad.

You also should be scanning it to see what the O2 sensors are doing and the fuel trims are doing.





 
Icon Legend Permissions Topic Options
Report Post

Quote Post

Quick Reply

Print Topic

Email Topic

425 Views
FusionBB
FusionBB™ Version 2.1
©2003-2006 InteractivePHP, Inc.
Execution time: 0.173 seconds.   Total Queries: 18   Zlib Compression is on.
All times are (GMT -0800) Pacific. Current time is 11:18 AM
Top