2005 B5 long crank to start

My wife's B5 has to crank an extended time to start. 10-20 seconds usually. It's not every time, but probably 90% of the time. It will restart immediately after shut off, but longer than 10 minutes and all bets are off. Once started, it runs perfect. There are no visible fuel leaks or raw fuel smells of any kind and all hoses are dry and in good shape.

Here is what I have done so far:
1. Removed access to pump in the tank and listened. It cycles with the key being turned on.
2. Removed supply hose from filter and observed fuel flow when key was cycled. Instantly fuel flowed for about 2 seconds and got about 1/2 cup.

All steps below had at least one drive cycle completed before the next step was performed.

3. Bypassed thermo "T" on filter. Made no difference.
4. I put a hand operated vacuum pump on the supply hose from the tank and just some fuel, no air flowed.
5. I put the vacuum pump on the return hose from the tandem pump and got mostly air.
6. I put clear hoses from the supply hose to the filter input, and from the engine return hose and the return to the tank hose (termo "T" still bypassed). When the key was turned on, fuel would flow from tank for about 2 seconds then stop. During cranking the fuel would start flowing from the tank again, but none could be seen returning to the tank. As the engine started to fire, then fuel and air could be seen in the return side. I let the car sit for a while, and then I did this a second time to make sure it wasn't due to air being introduced from putting in the clear hoses.

I am thinking the tandem pump is letting air get in the system when the engine is off.

Any ideas?
Chuck

Something to try would be to cycle the key several times prior to starting to see if the in-tank pump priming solves the issue. If that's the case, then the tandem pump (or an air leak) is the issue.

I would also remove the supply line from the tandem pump again, and also cap it air tight at the in-tank pump to make sure that line is not allowing air into the system.

We have tried cycling the key about 6 times. No change. Every time I've taken off the supply line from the in-tank pump at the filter, it has been full of fuel with no air. Only air I keep finding is in the outlet of the tandem pump, back to the filter.

If it runs fine once it starts as you have indicated, then I would suspect the tandem pump at this point, with a longshot chance on something electrical.

Yeah, unfortunately that's what I' thinking also. Thanks.

I had a similar problem with my B5 and replacing the tandem pump along with fine tuning the injection timing solved the problem. Same exact symptoms as yours but mine would not start at all after letting it set a few minutes. Ran great otherwise.
I picked up a NOS tandem pump off eBay for $180.

Thanks. I'll have to take a look. My injection timing appears to be great already, but worth a look.

ChuckV309 said:

Thanks. I'll have to take a look. My injection timing appears to be great already, but worth a look.

Click to expand...

Let us know what you end up doing. I'm having similar symptoms.
d

Going to order a new tandem pump. Just got to find the best deal. Any suggestions? Looked on e-bay and only found used ones. Looks like I will probably order one from the vendors on here.

Got the new tandem pump in over the weekend. Appears to have fixed it. Starts instantly like it should.

ChuckV309 said:

Got the new tandem pump in over the weekend. Appears to have fixed it. Starts instantly like it should.

Click to expand...

Nice!
Guess I need to start saving quarters...
d

Yup. they're not cheap, but it fixed it for me. My wife even ran the tank down pretty low to make sure and all is fine. I did make one little alteration while I had it off. I lengthened the fuel return line between the tandem pump and the fuel temp sensor by about 2 inches. The original line was so tight, that there was not much room to move the pump and remove the clamp and hose off the return nipple. Now the pump can lift all the way up to remove the clamp and line easily. Just make sure to use diesel rated fuel hose.

Did you notice any improvement in power after installing the new pump? I noticed a significant improvement in mine. I just returned from a 1300 mile round trip with the car and it ran great.

It's my wife's, so I couldn't really say. Asked her, and said not that she noticed. Of course she would barely notice if the engine was blown.

Ha! I know how that goes.