Hello all. Like the subject says, I have a 90 L98. It has low miles, but has been sitting for about six years without running. After an oil and filter change, gas tank drained etc., I cranked her up, but it didn't want to run without a booster shot (small) of starting fluid to get it going. Otherwise, just fast cranking and almost starting, but no dice.

I got it running and after tapping on the injectors, they all seem to be clicking now. After finally doing the correct test, I can see that I have low fuel pressure as in 16psi. I then did the hose squeze tricks and I can see that the in-tank pump is to blame. No leaky injectors even.

Could I get away with an external pump to act as a booster for the weak in tank pump? I just want to do it for a while, til I can go thru the agony of removing the tank to change the internal pump. MSD and Summit sell a very similar pump that claims it can create as much as 85psi for less than $100. Anyone think this will work temporarily?

 

Welcome aboard thirdgen.org.

There are two factors to fuel pump performance: pressure, and volume. Low pressure almost always goes with low volume. So, even if you could boost the pressure with the add-on pump, it would be short-lived since you still most likely couldn't produce sufficient volume.

The pump pick-up sock could be your real culprit, especially since the car sat for a long time. If that's the case, dropping the tank is the only way to fix it.

 

Thanks for the reply. Any thoughts on cutting a hole in the floor pan and installing an access door? Anyone here that has done that?

 

Gets discussed pretty often....

Pits people who don't mind hacking up their cars on the one hand, and people who like to preserve their cars' integrity with the minimum of compromises and do things right, on the other. Usually degenerates into a pointless flame war.

Bottom line however, is that hacking it doesn't really save much time.

To do it right, support the car with jack stands by the "frame", as high as it will go. The points where the LCAs connect makes a good support spot. Unblot the shocks and the sway bar end links, and let the rear hang down as low as it will go (you'll need to undo the brake line from the rear). Take the exhaust out; if it's aftermarket and has the usual junction, you can take it apart there, otherwise it's probably easiest to cut it at the first 6" long straight spot after it reaches it highest point passing over the rear, and use a slip-on "splice" to put it back together. Take out the Panhard bar, and the chassis brace that goes across above it, and the big heat shield between the muffler and the tank. Remove the plastic filler panel thing around the fill neck and the gas cap door (3 screws). Unbolt the tank, let it down a bit, and unhook all the lines. Let it the rest of the way down and have your way with it. It's easiest if you drain the tank first, and have something to let it sit on abotu 6" or so below its installed position.

It'd be a great time to replace the sway bar end links, shocks and the springs, since the springs will fall out and the end links will be out and the shocks will already be halfway out; the fuel filter, since you'll probably stir up a bunch of crud (and it's a good idea regardless); and whatever else you disturb in the process.

Should take maybe 3-4 hours, depending on how much trouble you have with rusted hardware and the exhaust.

 

ya just drop the tank and replace what u need. its not that hard, either way u would have to drop it to cut it... dont know why u would do that. also, get an adjustable fuel pressure regulator and set it to like 46 - 50 psi. its only like 60 bucks, takes about an hour and improves performance a lil. that should get u going.

 

Thanks guys, I guess I'll just suffer thru the work of dropping it. It's not like it's going to be the first time for this. I was just contemplating the horrors of doing it yet again in a few years. OTOH, I really don't want to cut up a pristine body. Now for the "might as wells".....you know...might as well just get a new tank etc.....

 

Im about to replace mine to,and Im not cutting a hole.Im replacing mine with the ac delco 1LE pump.

 

I took everything loose Saturday and pulled the tank out Sunday morning. It only took a few hours and I took my time with it. The gas tank is a leaking waste-case. Full of rust, the fuel pickups were rusty (again) and the sender was dangling. The sock was laying loose in the tank......pitiful.

I ordered a new tank from Rockauto for $175. Splurged on a new pulsator and even the ridiculously expensive "sending unit" assembly too since they had an aftermarket one for a somewhat reasonable price. It couldn't possibly be made any shoddier than the factory one, so I'm not too worried about the quality. I'm going with an EP381 pump. Hope it's not too much flow, but the stock one is way overworked and I wanted to try a higher capacity one this time.

Tank should be here tomorrow, pickups the next day and the new pulsator on Friday. Should be rolling by the weekend.

 

That's a good argument right there against the cut-a-hole method... I'd be willing to bet that a fair number of cars with bad fuel pumps, are like that or close to it, and aren't too far from needing the tank R&R'ed ANYWAY. Meaning, cutting the hole doesn't save ANY time at all, and actually ADDS TO the total burden of the project, besides being a hack job on th ecar.

 

Hey afremont, As was said before,dropping the tank is the way to go.The only
other thing I would add is get a buddy to help you.Taking the tank out alone is not too bad but I can assure you that your " lockerroom " vocabulary will
increase not only in volume and intensity but in creativity as well when you
try to reinstall it alone.



" The secret of life is honesty and fair dealing...
If you can fake that,you've got it made. "
Groucho Marx

 

I got it out by myself, but it took some finaggling to get the last 1/4" of the filler neck to clear a bracket. I've read that these replacement tanks don't have the filler neck bent to the correct shape, so that should make things even more fun.

 

Well, I got the fuel tank installed. My tank cam a couple of days ago and the pickup/sending-unit assembly came late yesterday. The cheap sending-unit from Spectra is at least as well made as the original Delco part, if not better. At least it came in a plastic bag to keep it nice and shiny.

I had to slightly modify the EP381 fuel pump and rubber seat to fit it all together. I didn't install a pulsator, I just did the rubber hose thing. To my amazement, the tank went right into place, but the filler neck is not quite in the right position. Someone stronger than I may be able to bend it slightly into place. I had trouble with one of the straps not wanting to adapt to the new tank; a few well chosen cuss words and my hammer persuaded the strap to cooperate. I left the lines disconnected for the time being.

I put five gallons of new gas and a half can of seafoam in the tank. I said a quick prayer, turned on the key and was rewarded with fuel dumping onto the ground. I connected the high pressure feed fitting and put a jar in place to catch the fuel coming out of the return line. I turned on the key and got my 2 second buzz and couldn't believe my eyes. Some nasty black goop mixed with something smelling sort of like gasoline poured into the jar. I did the key a couple of more times and decided that I better flush it good since it was still puking out black stuff.

I put a gallon milk jug in place and went to the front of the car. Lo and behold the fuel pressure gauge showed about 40PSI. Even better, it was holding pressure without the pump running. I applied my jumper to make the fuel pump run continuously and I let it pump the jug almost full. By then the stuff coming out had been looking nice and for a while. I connected the return line hose to the tank.

I turned the key and it cranked about two whole seconds before it fired right up. It seemed like a couple of injectors were sticking at first, but the engine smothed right out in just a few more seconds. I checked with my stethoscope and all the nearly 20 year old injectors were clicking away and the engine was purring. Alas it was now dark so I will have to wait til morning to reinstall the heat shields, exhaust, springs and shocks.

After doing all this on jack stands, my advice to people is "Don't cut your floor pan". It's really not that hard to do. It's really only a couple of hours work once you've done it.

Oh man I can't wait to drive it again, it's been over six years.