9020v

My 02 z06 had a non-operational fuel gauge when I bought it. Filling up with good gas fixed it, but it would still drop out sometimes. Clearing the error code brought it back to life temporarily. Previous owner told me I needed to clean the fuel sender. Eventually, one day I ran out of gas with about 3/8 tank indicated. Consulted this forum and tried a seafoam treatment in the gas. This time I ran out of gas just above 1/4 tank indicated. Consulted forum again and found the thread about the right tank jet siphon pump.

So, I pulled mine out and about 6 gallons came out of the right tank (this was after it "ran out" and I put in a half gallon to get home). I didn't check the left tank, but I'm guessing it will be near empty.

So I took the whole device and apparatus out and apart. I tried to blow through the jet siphon pump, and it seemed like I could, but who knows if I blew something out at first. The hole is so tiny it's very difficult to blow air through anyway. So I don't have any evidence to believe it was clogged. I was able to blow through everything else fine. Bottom of tank looks clean, but I'm not about to put a flashlight up in there to look closer.

So, if it's not this jet siphon pump, what else could it be? Do I need to check something in the left tank? Should I reinstall the pump and see what happens? I tempted to just buy a new one so I can eliminate that variable, but I have no evidence to support that it's bad except that my right tank dumped 6 gallons when the car ran out of gas. Which is another question, shouldn't it be running out of gas at 1/2 tank and not 1/4-3/8 tank? Is it possible my fuel level sensor in the right tank is bad? (but wouldn't the pump still run?)

Also, if I do put the old jet siphon assembly back in, can I use worm-clamps on the hoses that attach everything together, or do I need to use those special crimp style clamps that were on it before?

Thanks!

rebelheart

It often takes several doses with Seafoam or techtron to clean the fuel senders contact area.

9020v

Do you mean the fuel sender on the left side? I already have the whole assembly OUT of the right side of the tank and soaking in a glass of Techron. Trying to treat the problem by running additives in the gas isn't acceptable at this point. The car is on jacks and I need to decide if I need to reinstall the old jet pump assembly, buy a new one, or dig into the left tank.

Does anyone have any input on this?

Would a clogged fuel filter cause this problem? Fuel isn't getting transferred from the right tank when it's half full or so, but the jet pump assembly **seems** ok. Where else could the flow obstruction be?

9020v

Any ideas guys? I'm going to tear back into it this weekend.

Do I need to get a fuel system tester and test pressure between the right and left tanks?

So confused...

LoneStarFRC

From your description, I would recommend replacing the right-side assembly and replacing the left tank sending unit (only).

Carter pump assy part # for right side: P74894M $286.79 This includes a new tank flange gasket and screws.

AC Delco sending unit for left tank: SK1318 $95.79 I'm almost positive this part does NOT include a new tank gasket and I would highly recommend replacing the old one so therefore, order an AC Delco G25 gasket (w/screws). $39.79

Note: Follow the criss-cross tightening sequence for the (6) tank flange fasteners on each side, and if they are the same design screws as the originals, do NOT overtighten. They should be torqued to (IIRC) 22in lb (That's INCH pounds), but double-check that number, I'm going by memory here on that one. If the new screws are the breakaway type (they come in the AC Delco G25 gasket package) they are self-torquing. Don't need a torque wrench for them. The head automatically snaps off when torque is reached.

BTW, the prices are from Rock Auto's website. If you do decide to order anything from them let me know and I have a 5% discount code good through Aug 28th you can use.

HTH

9020v

Sure, I'll take that coupon code and order those parts unless you think the dealer would be cheaper. I haven't tried pricing anything yet.

I was going to try and put the assembly back in and see what happens after soaking for a week in techron and pulling a wire through the hole, but I'd kind of rather do the shotgun approach and put new parts in so I hopefully don't have to dig into it again.

But, regarding the screws, I already stuck the flange back in the tank so that it would not be exposed while I was working on the assembly. I already hand tightened the old screws down (surely overtight!) just to hold it in place. I wasn't aware they were 1-time use only and had a crisscross pattern. Also, I put the original gasket back on, which isn't exactly circular, it is flat on 2 parts, and I didn't know how to orient it. So you're saying replace the gasket and screws, I'm fine with that, but did I screw anything up by sticking the flange back in there temporarily and overtighetning the original screws in a clockwise sequence?

Thanks!


Edit: N/m about the coupon - I just ordered these from Amazon and eBay for $375 total. Not too bad I suppose. So what is the procedure/orientation for installing the new seals and senders? I have the shop manuals on order too, but these will get here before they do.

LoneStarFRC

As long as you didn't strip the brass threads in the bolt holes you should be OK, but just to be on the safe side you may want to go back and loosen then re-snug just enough to close the opening for now.

The OEM screws are not the break-away type. They are the regular type screws. It's the replacement screws that are of the breakaway type. They are very convenient as far as not needing a torque wrench and it's impossible to over-tighten them. The instruction sheet that comes with the new gasket package shows the correct orientation of the "flats" on the gasket as well as the tightening sequence. In the picture that Carter (well known and respected company) provides online for the right side pump assembly, they show the gasket and the screws they provide with the pump are the same as the OEM (non-breakaway) screws. No biggie really, just carefully tighten them to the proper torque and you're good. Considering the repercussions of possibly over tightening them by "hand" (fuel tank replacement = $$$$$) I would either buy or at least borrow a torque wrench for these screws. Either a 1/4" drive or a 3/8" drive is fine, as long as it can be set for the correct low inch-pound settings. Edit: found the correct torque: 62 inch-pounds (Lingenfelter's website for fuel pump replacement instructions).

If you want to check with the dealer on these items, be sure and bring your nitroglycerin tablets as you're likely to experience cardiac arrest. Seriously though, even though there are actually several sources for these parts, I have found that on many (but not all necessarily) occasions, Rock Auto has good pricing and they are fast shippers and do not beat you up on shipping costs. I've used then several times over the years and no problems.

LoneStarFRC

Go to Lingenfelter's website (LPE) and checkout their installation pix for their fuel pump. It shows how to get the LH fuel pump module part way out then unclip and remove float/sending unit before pulling the rest of the pump module out. It's a bit tedious but not hard to do.

9020v

Awesome, thanks you have been a huge help!

I hope this solves my fuel problem. The only other thing I could think is that the line between the siphon pump and the left tank is clogged somwhere (either feed or return). Not really sure how to test that though... hopefully I won't have to!

LoneStarFRC

It's a 3/8" line so it's not clogged, but if it'll make you feel better, blow through it. The small orifice hole in the right-side siphon-jet MAY have had some debris in it, but I think even that's unlikely since all fuel sent to the right tank is sucked through the filter sock on the left-side fuel pump first. The outlet line of the right tank goes directly to one of the three connections (an inlet) on the left tank. It's the only inlet, the other two are both outlets.

9020v

So itś more likely that the senders were bad? I understand why that would cause the fuel gauge dropout, but dont understand why it would empty the left tank and leave 5 gallons in the right tank.

Just curious as to your thoughts of where the failure is occuring.

LoneStarFRC

In the end, I think it's likely a combination of things. Sender(s) being contaminated with sulphur deposits, varying levels of alcohol due to a particular location(s) in the country where different "boutique" blends of gasoline are mandated by different state laws, and they often change back and forth from summer to winter, not to mention the normal variation in "top tier" gasolines vs lesser quality being sold by different refiners/retailers (also remember the PCM is programmed to see and "expects" to see the right side fuel level to drop before the left), bad/failing electrical pump, plain 'ole ordinary "crap" contamination from dubious fuel sources partially clogging/restricting the filter sock(s) (in the right tank especially), etc.

For example, one thing I noticed is that the new right side siphon-jet module I installed has two small wire-mesh "cylinders" that are the filtering screens for the fuel from the right tank to go through before being sent to the left tank and the original had two fine mesh filter "socks" like the left tank unit uses. To what degree this may affect the transfer flow rate of fuel from the right side to the left side I'm not exactly certain and then it may just be a later ("better"?) design version from GM. One things for sure though, if the fuel from the right tank is not being transferred to the left tank in sufficient quantity while motoring down the road, eventually the left tank is going to go "dry" and you will be on the side of the road. Back when I was experiencing all this, I "ran out" out of fuel twice.
What a PITA.

Dale002

You are going in the right direction. Seems like the jet module is acting up,but also check what makes it work as well to see if there is a problem there. Do you a set of manuals?

9020v

The unit I pulled out my right tank did not have the socks, but rather the screens like your replacement had. I don't know if that makes any difference, we shall see!

LoneStarFRC

Since you're not afraid to get in there to work on this system, I can think of one other thing I would personally recommend that is relatively cheap and has good long term reliability benefits by improving on the OE set-up. This applies to guys with highly modded engines or stock, either one.
Racetronix makes a direct-wire harness for the C5 that supplies power to the electric pump directly off the hot post on the alternator. Some call a "hot-wire". It's high quality and uses correct Delphi Metri-Pack connectors, etc (direct plug-n-play, no cutting, etc). Eliminates any possible voltage drop/poor ground issues with the fuel pump, guaranteeing full voltage at all times. Voltage drops = lower pump output. Comes with a fuse and relay pre-wired. I ran the wire loom through my rocker panel and out by the brake booster then under the left fuel rail cover to the alternator.
Very well made. I have been very impressed with the quality of their electrical harnesses/adapters and such. They truly know what they're doing. You can buy direct through them or one of their distributors such as Texas Speed, Thunder Racing, etc.

9020v

I'll think about this tonight. Lack of fuel pressure certainly would explain improper operation of the siphon pump. What about the filter sock on the fuel pump in the left tank? I haven't got into the left tank yet, but would that be a potential source of my problem? Why don't you think I needed to replace the LF fuel pump but just the sender?

LoneStarFRC

For the most part these electric pumps seem to be pretty durable. I'm not aware of any wide-spread failure problems, etc. not to mention the obvious fact that the pump appears to be providing fuel properly and the engine runs fine, at least until it "runs out". Measuring the pressure at the fuel rail (normal is 58 psi nominal) is always a good thing when doing diagnostics as well as ensuring the ground point at the left rear frame is clean and tight. Another good thing about the hot-wire mod is that it really helps eliminate any ground issues but as always, good visual inspection and common sense are needed too.

As cheap as they are, a new filter sock in the left tank is a good idea. Of course then you're going to have to pull the complete unit all the way out to get to it.

Btw, I think your concerns about flashlights and fuel tanks is not realistic but if you're really concerned you can always "seal" the flashlight in a clear plastic Zip-Loc baggie first, then shine it inside the tank.

9020v

According to the papers the new part came with, the torque is 6.5 N-m +/- 1 N-m. So, that's 57.5 in-lbs. I probably put it to 60.

Unfortunately I didn't put enough gas in to start it, so I killed the battery and am waiting for it to charge before the hurricane drops a tree on it.