I bought this 99 24V 3500 about a year ago. First I put gauges on it and found the fuel pressure to be low, 3 on hard acceleration, but the truck ran OK. I changed to a DDRP and bigger line, bled out the air at a couple of injection lines and it started up and ran even better. Pressure at the filter housing is now up at 30 on startup, however, it no longer starts on the first crank, but after about 10 seconds, release and recrank and it starts. The filter was recently changed, Lucas additive has been added to the fuel, and slowly it seems to be getting harder to start and now never starts on the first crank, usually on the second crank, but sometimes takes a third crank effort. But it doesn't miss, runs good going down the road once started. The CEL has been on since I bought it with codes of P0230 (Transfer pump circuit out of range), P0113 (Intake air tem sensor voltage too high) and P1693. I've cleared them previously, but it seems they reset practically instantly. Yesterday I plugged in the DRB Chrysler machine and the codes have had 89 starts since triggering (all 3). However, it would not let me clear the codes, either with the truck running or not. I also checked the Engine RPM and Inj Pump RPM and they're =/- 2 rpm as are the engine speed ckd and Cmp Sensors, so that doesn't seem to be the issue. Ironically, upon relooking at the codes, now they list 1 start since triggering. The truck has had a relay bypass wired into the lift pump circuit at some time. I've checked for the return line leaks but haven't found any fuel leaking.

So can anyone enlighten me with the strong crank/slow to fire condition and/or point me in the right direction to correct these codes? Let me know what other info might be useful and I'll try to obtain it. Thanks in advance for any assistance!

 

From what I have read on here, 30 psi is way too high for fuel pressure and will cause hard starting.

As far as the codes, it would depend a great deal on how your aftermarket fuel pump is wired in. It sounds like the PCM is seeing an open circuit with no lift pump in place.
The IAT code sounds like it is seeing an open circuit somewhere, and it would be helpful if you had the scanner attached during diagnosis, to see what the ECM is seeing as sensor voltage. Have a look at the IAT sensor connector first and make sure that's not the problem.

 

[QUOTE=torquefan;2968357]From what I have read on here, 30 psi is way too high for fuel pressure and will cause hard starting.

i agree, if you have 30 lbs cranking pressure you need to reduce it to 15

 

When exactly does it hard start? Does it do it all the time? Does it do it only after the trucks been sitting for awhile and the engine is cold(er).....like after all day at work or after sitting all night? Does it only do it only after the engine is fully warmed up, like shutting it off at the gas station or running in a store and then trying to restart? Its important to know specifically.

Do you also know what your FP is during cranking alone? I agree that 30 psi while running is excessive, as is anything over 20 psi, but your running FP wouldn't be the problem. You either have an air leak in the return side of the fuel system or the excessive cranking pressure is causing your problem. But then you also mentioned that the truck has a bypass relay wired into the fuel pump loom. Are you sure that its a bypass relay or is it merely a power relay so that the ECM is no longer having to power the fuel pump directly anymore but merely sending a signal to the relay?

 

Thanks for the help guys! Sounds like the 30 PSI during cranking is too much and I'll need to pickup a regulator. Adding the regulator under the truck by the DDRP on the frame rail would be the easiest, or would you all recommend closer to the injection pump?
Katoom, as for when it does it, ironically, cold starts are easier than warm starts. If I go into Home Depot and come out 30-45 minutes later its much tougher than a cold startup. And looking at it, I think you're right about the relay, seems more like bypassed the ECM and straight to a hot lead when the key is on. This is probably my CEL then. So let me start with a regulator and see what that does - everyone agree on 15 or 20PSI?

 

Optimal fuel pressures are about 20 psi at idle and 15 psi WOT. Just over 20 isn't going to harm anything but if you ever get close to 10 at WOT then you need to be concerned. As for the regulator, it doesn't matter where you mount it, as long as its mounted before the FP gauge BUT.....you need to contact FASS because they shouldn't have let a DDRP leave that was putting out that kinda pressure. FASS will/should either tell you how to fix it or send you something to fix it. Also, are you absolutely positive that your FP gauge is even accurate? If no then maybe you should find a test gauge to compare. I'm not doubting the capabilities of the DDRP but FASS clearly knows the fuel pressure parameters of these fuel systems so I'm giving them the benefit of doubt. Then how is your relay wired in? Is one of the relay pins left open and unused?

 

Thanks for all the help. The relay does have one pin not in use and thus is Hot, Ground, Fuel Pump, and Ignition only. The ignition wire is an extra wire pulled from the ignition switch and is "on" during running and cranking. I quickly disconnected the relay yesterday when it cranked but wouldn't start and it instantly started right up, then I reconnected and all was well. So obviously the PCM is no longer triggering the fuel pump, causing the codes and too high fuel pressure during cranking. I've intercepted this additional wire from the ignition with a toggle switch to the lower hush panel for now to turn it off before cranking and so far this has worked without fail. I still have 32 psi at idle and mid-high 20's cruising the highway. I bought the pump from KLM, but can't get them to call me back, and can't find a number directly to FASS - can anyone pass it along to me as I'd like to discuss the issue with them (2 gauges before and after filtration) and their recommendation on a regulator? Thanks again for all the assistance folks - this site is fantastic!

 

I also have a DDRP in my truck and I had a question about one of the gages and I called Isspro direct. There was a number in the directions with the gage. They were most helpful and we got things working. My gage read 22-24 at idle and no less than 10-12 at WOT. I have also noticed hard starting lately, truck used to start on first turn of switch but now takes a little longer on the starter. I will follow your thread with interest.

 

Sorry that KLM isn't calling you back. That doesn't sound like good costumer service, but I always try to give the companies the benefit of doubt since maybe they're so busy that they just haven't had time to get back to you. No that doesn't make it right either.

I'd still make sure that your fuel pressure gauge is accurate since your fuel pressure seems very excessive and should have been set to regulate a lot lower than that when you got it.

If your fuel pump is pumping to much during cranking, causing a hot start issue, then you can install a relay, following the diagram pictured, and your the truck will start like it should. BUT.....you need to confirm that your starting issues are from excessive fuel pressure during cranking and not from a fuel leak otherwise the relay will not fix anything.

 

As a retired electronic engineer and long-term 2nd gen. owner with the VP44, I can not recommend the circuit posted to power an after-market lift pump. The "piece of junk" Carter pump that came mounted on the engine drew a maximum of 4.5 amps from the ECM. The ECM provides power to the lift pump by using FETs (Field Effect Transistors) and a computer is used to slow the lift pump to provide only about 7 PSI as the engine cranks. This was necessary to prevent hard starts because the Carter pump will put out 15 PSI when running at 12 volts. The circuit provided above shows the ECM connected to a relay to provide power to the lift pump as the engine is cranking and not with the key "on". That is fine but the problem is when using an after-market lift pump will the current draw from the ECM be greater than the "piece of junk" Carter? Most non-stock lift pumps will draw more current from the ECM and need a relay to provide the extra current.

The intent of the circuit is sound. It will delay the lift pump until the starter motor is cranking the engine and will limit fuel pressure because the battery voltage is lower when the starter is engaged. The problem comes when the ECM is asked to supply a greater current to an after-market lift pump. How do you feel about replacing your ECM because the FETs got fried?

Optimal fuel pressure is a long-standing matter of opinion. Cummins limited the fuel pressure to about 7 when cranking and the "piece of junk" Carter never made more than 15 PSI. Something tells me higher pressure may not be bad but is it necessary?

 

bent valves, because you were an electronic engineer, I will give you the benefit of doubt in that you must have overlooked what the diagram is actually doing. And I also appreciate your concern too.

When someone installs an aftermarket electronic fuel pump (FASS, Airdog, Raptor), the pump comes with a wiring loom which relieves the ECM from its job of "powering" the fuel pump by using its own switch power relay. The ECM still "controls" the fuel pump by switching fuel pumps relay on or off. The relay in the diagram is simply an additional relay which interrupts the signal coming from the fuel pumps power relay so that the fuel pump does nothing while the engine is cranking. Not only is this perfectly fine but its also what the VP prefers. There is even a factory flash which performs this very task. I'm sure I completely botched up the description too but just be assured that the ECM is protected if the posted diagram is utilized with an aftermarket fuel pump.

 

OK, so the yellow/white wire in the diagram should not be connected to the lift pump. Maybe Mopar1973Man said that a relay must be used where the lift pump is drawn.

 

Yes, the yellow/white wire does go to the fuel pump but.....why I can see where you would misunderstand the diagram is that if you have an aftermarket fuel pump mentioned then there is another switched power relay (not pictured) connected to the ECM with Y/W wires via the new wiring loom. So like I described before, the diagram is only a relay to interrupt the power to the fuel pump from the aftermarket power relay. Again.....I did a crappy job of explaining it. I agree with you too that the ECM should NOT power a fuel pump. I think that even the factory set up is poor and there should have been a relay in place to keep the ECM from doing anything but telling the fuel pump when to pump.