Fuel check valve and the 3port fuel pump Options

[brant]

I think there must be a check valve built into the 3 port djet pump

I believe mine is not working
(Hard starting symptoms)

Has anyone pulled theirs apart?

Pictures or a thread?

I'm also wondering if adding an in line check valve would work?

[brant]

So Brad Anders website indicates their is a check valve in the fuel pump and that there have been instances of them failing...

unfortunately the URL's on his page are not working:
Fuel Pump •Function: Supplies fuel to the injectors and cold start valve.
•Failure Modes ◦No pressure/inoperative: Can be due to electrical or mechanical failure. The engine will not run in this condition. See the URL below for a test procedure.
◦Improper fuel line hookup: Very odd problems in maintaining pressure, with odd drivability problems. Check the factory workshop manual for the correct hookup.
◦Clogged return line: I had this happen when I converted back from carburetors, my return line was clogged at the tank. High fuel pressure and rich, possible gas contamination of oil. If you can't regulate the pressure, this may be your problem.
◦Failed Check Valve: The check valve keeps the pressure to the injectors and CSV up after the fuel pump is shut off to prevent vapor voids from forming and speed up starting. A failed check valve may cause some hot starting problems. There has been one report of a failed check valve causing the fuel pump to return all fuel to the tank, with no supply to the injectors. See the URL below for a test procedure.

•Notes: Detailed procedures on checking the fuel pump are documented in the Factory Workshop Manual. The electrical plug, contacts, and boot are often in poor condition due to exposure to heat, battery acid, and the environment. Contact failures are a common cause of a sudden shut-off of your car while driving. You should hear the fuel pump run for 1.5 seconds after turning the key to the "on" position. If you don't hear the pump run, check the fuel pump relay on the relay board, and the connection plug to the fuel pump. I keep a cheap Radio Shack multi-meter in my car just for this problem.
•More: There is an excellent reference on debugging fuel pump problems at the URL below:


http://www.914fan.net/fuelpump.html

I also have created a series of flow charts for diagnosing the fuel pump circuit and relays:

http://members.rennlist.com/pbanders/FPChecklist.htm

[BeatNavy]

◦Failed Check Valve: The check valve keeps the pressure to the injectors and CSV up after the fuel pump is shut off to prevent vapor voids from forming and speed up starting. A failed check valve may cause some hot starting problems. There has been one report of a failed check valve causing the fuel pump to return all fuel to the tank, with no supply to the injectors. See the URL below for a test procedure.

Brant - I have similar experience on an otherwise generally well-running 2056 D-Jet. I've wondered the same thing about a check valve. I bought my fuel pump rebuilt from AA a couple of years ago, but I'm thinking about changing to that Bosch 2 port unit.

Can someone confirm: should the fuel pressure in the system STAY ~29 psi even when the pump is off (or maybe bleed down slowly)? Mine does not. It bleeds off right away. My other symptoms:

1. Takes me about 5 seconds of cranking to start when it's cold, and I ALWAYS have to feather it once or twice during the first 10 seconds of running or it will die one time. If it does die, it will immediately fire up with turn of key and stay started.

2. If I kill engine and IMMEDIATELY restart, it fires up with no problem.

3. If stop briefly for a few minutes, e.g., to fill up gas or run quickly into a store, it may take 5 to 15 seconds of cranking and then will idle so low for 20 or 30 seconds that I normally have to feather it to keep running. After that, idle picks up and all good. It doesn't seem like it's that "warm start over-enrichment" issue, because the head temp is still high, and my O2 is showing more like 14+ at that point.

This morning after a 20 minute doctors appointment. I started the car with accelerator depressed, and it did seem to help it start more quickly and stay started.

Maybe I'll put replacing the fuel pump on my to-do list and see if that helps.

Also, I've tried to go to that P914fan.net link before hoping to get answers, only to find a "fitness fan blog." And Brad's fuel pump page isn't working the way it's supposed to anymore (I think it may not be compatible with modern browsers). I know he's been active here recently - I don't know if he's got the time to update it or not, but it would be appreciated (IMG:style_emoticons/default/pray.gif)

[87m491]

I don't know D-jet at all compared to my CIS cars but I think it would stand to reason that residual pressure might bleed off but not drop to zero like flipping a switch.

5 Seconds to start from cold could be almost anything, then feathering might point to another tuning issue as the whole purpose of F.I. is to preclude this issue. Most of what I have read and experienced on D Jet is a high initial idle with a drop towards normal once warm.

Killing and re-firing instantly doesn't sound too surprising with everything else, pressure may be bleeding off but every turn off the key on fires off the pump with a short prime pulse giving you back "full" pressure after the quick shut down.

Your short stop scenario is like classic CIS vapor lock or pressure bleed down via a bad check valve. Since after the initial prime the pump won't run unless it senses the engine running and of course the engine won't run without higher fuel pressure. Many will hard wire the pump to run with the ignition on circumventing the speed sensor, and causing a safety hazard.

If you can't find a source for the "pressure leaks" I'd say get the new 2 port pump and be done with it.

Brant - I have similar experience on an otherwise generally well-running 2056 D-Jet. I've wondered the same thing about a check valve. I bought my fuel pump rebuilt from AA a couple of years ago, but I'm thinking about changing to that Bosch 2 port unit.

Can someone confirm: should the fuel pressure in the system STAY ~29 psi even when the pump is off (or maybe bleed down slowly)? Mine does not. It bleeds off right away. My other symptoms:

1. Takes me about 5 seconds of cranking to start when it's cold, and I ALWAYS have to feather it once or twice during the first 10 seconds of running or it will die one time. If it does die, it will immediately fire up with turn of key and stay started.

2. If I kill engine and IMMEDIATELY restart, it fires up with no problem.

3. If stop briefly for a few minutes, e.g., to fill up gas or run quickly into a store, it may take 5 to 15 seconds of cranking and then will idle so low for 20 or 30 seconds that I normally have to feather it to keep running. After that, idle picks up and all good. It doesn't seem like it's that "warm start over-enrichment" issue, because the head temp is still high, and my O2 is showing more like 14+ at that point.

This morning after a 20 minute doctors appointment. I started the car with accelerator depressed, and it did seem to help it start more quickly and stay started.

Maybe I'll put replacing the fuel pump on my to-do list and see if that helps.

Also, I've tried to go to that P914fan.net link before hoping to get answers, only to find a "fitness fan blog." And Brad's fuel pump page isn't working the way it's supposed to anymore (I think it may not be compatible with modern browsers). I know he's been active here recently - I don't know if he's got the time to update it or not, but it would be appreciated (IMG:style_emoticons/default/pray.gif)