False Starts and Aftermarket Parts

"Urambo Tauro" (urambotauro)
10/23/2017 at 12:00 • Filed to: Saab 900, Project, wrenching

We weren’t as close to starting the Saab as I thought.

There wasn’t much left to put back together. All we had to do was put the pump in the tank and the tank in the car, hook up the lines and wires, pour some fuel in, and start it up, right? Wrong.

Once the tank was back in, I poured a few gallons of fresh fuel in while my brother installed the pump. We slid some new O-rings onto the pressure and return elbows and pushed them into the hat.

But they wouldn’t seat all the way. They were tight, but way too tight, way too soon. Something was hanging up. So we yanked them back out to check for interference, but only one popped out unscathed. The elbow for the pressure line broke, leaving the plastic tip tightly wedged inside.

So we pulled the pump back out to take this fight over to the workbench. After much cutting, prying, and drilling, I managed to spin the last bit of the old check valve elbow out. My brother ordered up some new elbow valves (only needing one, but fearful of the other breaking) and I took some measurements.

Finally got the tip of the old valve unstuck from the hat bore.

The bores for the valve elbows were smaller than those on the old fuel hat. Not like “the next size down” smaller, but more like an error in manufacturing tolerances. It wasn’t a different size for a different application; it was built wrong at the factory. Close, very close, but just far enough to cause a fitment issue.

I double-checked the new valve elbows, which were of the same aftermarket brand as the pump. The tip of the valve was the same size as the originals, but the barbed end was a different size, needing an adapter to connect to the fuel line. What a pain!

Found an adapter and some tubing to make it work

Anyway, back to the pump assembly. The new valves would not fit in the bores of the new pump assembly. I could feel the plastic starting to wedge into place, whereas on the old hat’s bores, only the O-rings gave resistance (for sealing).

This was of course an aftermarket pump assembly, attractively priced at around $100, as opposed to the $300+ it would have taken to get an OEM Saab or Walbro unit. Despite all this frustration, we decided that it was still worth avoiding spending that extra coin. And we didn’t want to go through the hassle and delay of arranging for an exchange with the vendor, so we decided to stitch part of the old pump assembly onto the new.

Also note the orientation of the plumbing between the two pump assemblies. There’s plenty of flex in the new one to make it work, but the old pump’s tubing is tucked up closer to the body. The new one takes some maneuvering to get right.

That meant frankensteining the hat and wiring from the old pump assembly, and attaching it to the new pump, basket, and plumbing. After replacing some tubing and clamping it tightly with ear clamps, we had ourselves a pump that could actually be plugged into the car.

We primed it and sent some fuel towards the engine. But alas, several cranking attempts would not start the car under its own power. It would still respond to ether, but not fresh gas. Damn, I thought we had this in the bag.

The tank is clean, the pump is new, the lines are clear, the filter is new, the injectors are clean and their solenoids work... we never did check that fuel pressure regulator, though.

And wouldn’t you know, even though the pump delivers fuel towards the engine, nothing is coming back through the return line. Hmm... So we’re thinking that maybe the regulator is clogged with the same ugly mess that we found in the tank. OR... maybe this cheap Taiwanese pump isn’t all it’s cracked up to be (wouldn’t surprise me, based on what I’ve seen so far). Maybe it’s not generating enough pressure for the regulator to relieve?

We’ll have to attach a fuel pressure gauge to find out. Shame it doesn’t have a Schrader valve anywhere for that...

But maybe there’s more to it than just fuel pressure. We pulled the spark plugs, and found that they were all dry. But the injectors DO work- we tested and cleaned all four of them. Are they... not getting power?

Must investigate further.

DISCUSSION (15)

BahamaTodd > Urambo Tauro
10/23/2017 at 13:17

I’m a development engineer for aftermarket fuel pumps. It’s truly scary how much garbage is out there. If you want to go aftermarket, a good rule of thumb is to buy the most expensive one (assuming the original OE module hasn’t just been re-boxed).

What brand is that module?

BahamaTodd > Urambo Tauro
10/23/2017 at 13:35

If there is a clog somewhere in the system, you should be able to hear the relief valve in the fuel module (assuming you can get an ear close enough to the tank).

Urambo Tauro > BahamaTodd
10/23/2017 at 13:44

Professional Parts Sweden AKA Proparts .

We also noticed that the bright white plastic used for the basket and hat is thinner and more flexible. It’s kind of slippery too (PE? delrin?). The lock ring is made of the same stuff, and we did break a couple of the tabs during installation. We still used the new basket, but handled it delicately to avoid breaking it. I’m glad that we saved the old parts.

We were originally going to re-use the entire old assembly and just throw a new pump motor in it. But we couldn’t find new rubber isolator bushings, which had all but “melted” away in the old gas. So my brother just ordered a whole new assembly, which saved us from cleaning the gunk out of the old one.

Urambo Tauro > BahamaTodd
10/23/2017 at 13:48

Yeah, could be a bad valve there. After breaking the pressure valve, my brother ordered both elbows (pressure and return valves), so we do have a new return valve ready if we need it.

But we disconnected part of the return line closer to the engine, and verified that nothing’s coming out of the regulator. So we’re pursuing that first.

shop-teacher > Urambo Tauro
10/23/2017 at 15:48

It’s so frustrating when your shiny new part doesn’t actually fit where it’s supposed to fit or do what it’s supposed to do.

Urambo Tauro > shop-teacher
10/23/2017 at 17:07

Yeah, it sucks not having many options between expensive OEM quality and cheap junk.

shop-teacher > Urambo Tauro
10/23/2017 at 22:18

Definitely. Usually on a DD I just bite the bullet, but on a project like this it’s easier to justify spending time instead of money.

Akio Ohtori - RIP Oppo > Urambo Tauro
10/26/2017 at 16:08

Have you checked for spark? I know everyone always asks that... but there is a good reason. If the injectors aren’t injecting could be a problem with the hall sensor or crank position sensor or whatever your fancy 16-valve nonsense has. :-P

Urambo Tauro > Akio Ohtori - RIP Oppo
10/26/2017 at 16:15

Sort of. We’ve just been assuming that spark is good since it responds to ether. Maybe a more definitive check is in order. I can’t seem to get the ether application quite right to run it for more than a second or two, so we haven’t even confirmed that all cylinders will fire.

Akio Ohtori - RIP Oppo > Urambo Tauro
10/26/2017 at 17:15

Hmm that makes some sense. Fuel pressure is certainly a good thing to check. Really anything that has had fuel in it for any length of time is suspect at this point. Unfortunately this is where our cars differ significantly, so I can’t speak much more intelligently than that.

I do have the factory service manual PDFs for that car, if those would be of some help.

Urambo Tauro > Akio Ohtori - RIP Oppo
10/26/2017 at 17:45

Does it differ from the Bentley book? We’ve been getting a lot of use out of that, but have also found it to be lacking in a few areas (like dash fastener locations).

Akio Ohtori - RIP Oppo > Urambo Tauro
10/26/2017 at 18:41

As far as I can tell the Bentley is derived from the factory service manuals. That said, the factory manuals several feet of book... so they’re a bit... more... than the Bentley.

Kinja'd!!!

Urambo Tauro > Akio Ohtori - RIP Oppo
10/26/2017 at 18:53

Whoa, that puts in into perspective! Haha nice.

Yeah, let’s give it a shot. Do you have a link, or is it something that would have to be sent via e-mail?

Akio Ohtori - RIP Oppo > Urambo Tauro
10/26/2017 at 19:52

You can grab them here .

There are two sets (not sure why, not my dump) and some misc stuff too. Not 100% complete either, but it is the most I’ve found so far. Comment when you’re done and I’ll close the link. (Not sure of the ethical/ legal/ bandwidth implications of sharing this openly)

Urambo Tauro > Akio Ohtori - RIP Oppo
10/26/2017 at 21:52

Ok, got it all. Feel free to close it. (If you want, I can dismiss your comment, too)

Holy cow, that’s quite a collection! I’ll go through it later. Thank you!