Starting Problem

[ccurzio]

I've been having a weird problem as of late and I'm hoping someone can point me in the right direction at getting this particularly frustrating problem fixed once and for all.

A few months back I replaced my fuel pump with the new combo pump/sender unit from DMCH. I'm still a big fan of this unit and would recommend its purchase, despite its fairly limited warranty. That being said, while the car was running great after the initial pump replacement, after some time things started acting a bit weird.

I've titled this thread "starting issue" because I can't really tell if it's a hot start problem or a cold start problem. When I first got the car and immediately after I replaced the fuel pump, the engine would start with a single crank on the ignition. It was nice! But suddenly I'm having an odd situation. Here's what's up:

1. I start the car. It no longer starts on the first turnover but it'll typically get going after five or six cranks.
2. I drive for a while. Lets say an hour.
3. I stop the car and let it sit for a while. Lets say 3-4 hours.
4. I go back and try to start the car. It keeps cranking and cranking but the engine refuses to start. I can usually coax it into starting by trying a few times and pumping the gas pedal, but it usually takes several attempts.
5. Letting the car sit for an even more extended period of time resets it to the condition present in step 1.

It should also be noted that once the car is actually RUNNING, it seems to run fine. No bucking, no hesitation, it runs without any issues.

Obviously I'm leaning toward this being more of a "hot start" kind of issue just because it has to have been (somewhat) recently used for the issue to show itself. It should also be noted that if I were to stop the car after step 2 and then try and start it within a few minutes (REALLY hot start), it starts just fine. It's only after it's been sitting for a little while longer than that when the problem surfaces.

Since I am leaning toward it being more of a hot-ish problem rather than a cold-ish problem, I do have a new fuel accumulator and distributor O-ring on order from DMCH. But I would like some other opinions since I am still pretty new to this stuff.

Thanks!

[ccurzio]

Also this: http://dmctalk.org/showthread.php?4426-GNDN-Hose-(What-is-it-)&highlight=Fuel+smell

Note the bit about the fuel smell. Still haven't tracked that down entirely but I think I may have improved it.

[Bitsyncmaster]

Does it have the problem after a 1 or 2 hour stop after a long drive?

[ccurzio]

Yes. The problem begins to surface after about an hour but at that point it is still relatively easy to start. It progressively gets worse the more time it sits.

Then something happens to reset it, and the next day it reverts back to being somewhat okay.

[Bitsyncmaster]

You can test how long you hold rest pressure by pulling the air cleaner off after you shut off the engine. Then just tap the air plate with your finger to test for pressure. Don't press the plate down, just feel if there is pressure. I've found you need pressure for 4 hours in the summer months to prevent hot or warm start issues.

[ccurzio]

I actually bought a fuel pressure gauge yesterday to test for that very condition. (It won't actually arrive until Tuesday of course.) I wish I'd known it could be tested so simply, but it'll still be a handy tool to have around.

Assuming it is a pressure problem, what would be causing the condition to be at its almost-worst after four hours (with five to six being pretty much the worst) and what is causing the problem to go away after the car has been sitting for a day?

And then how does one correct such a problem? Am I on the right track with the accumulator replacement?

[ramblinmike]

After the car sits or a day rest pressure isn't an issue. When the car is cold the cold start injector fires as you engage the starter, giving an immediate source of fuel. When the car is hot the cold start injector doesn't fire and the car is supposed to rely on the fuel pressure in the system held by the accumulator. If the accumulator or the o-ring in the fuel distributor is bad rest pressure isn't maintained. When the starter is engaged there isn't an immediate source of fuel.

[ccurzio]

After the car sits or a day rest pressure isn't an issue. When the car is cold the cold start injector fires as you engage the starter, giving an immediate source of fuel. When the car is hot the cold start injector doesn't fire and the car is supposed to rely on the fuel pressure in the system held by the accumulator. If the accumulator or the o-ring in the fuel distributor is bad rest pressure isn't maintained. When the starter is engaged there isn't an immediate source of fuel.

This was exactly my thinking (which is why I ordered the fuel gauge, o-ring, and fuel accumulator), though I also wonder why I'm not getting that "instant start" that I had when I first got the car or when I replaced the pump.

I suppose if the accumulator is bad and the fuel system draws from that part first (CSV or not), then that could still explain the issue, yes?

I suppose the TTS can also be having problems, but I also happen to have a brand new spare one of those as well. I'll start by replacing the accumulator and see where that gets me, then the O-Ring if there's no luck.

[ramblinmike]

From what I understand, the TTS doesn't fail all that often. Besides, if it was bad, wouldn't you have a cold start issue? If it failed in such a way that the CSV was firing all the time, you would probably notice it running rich on a hot start.

[Bitsyncmaster]

If you have an original accumulator, it's best to get it changed anyway.

[DMC5180]

This was exactly my thinking (which is why I ordered the fuel gauge, o-ring, and fuel accumulator), though I also wonder why I'm not getting that "instant start" that I had when I first got the car or when I replaced the pump.

I suppose if the accumulator is bad and the fuel system draws from that part first (CSV or not), then that could still explain the issue, yes?

I suppose the TTS can also be having problems, but I also happen to have a brand new spare one of those as well. I'll start by replacing the accumulator and see where that gets me, then the O-Ring if there's no luck.

Does your RPM relay have a Priming function? Do you have OEM or DM-eng (SS relay) If so, you should theoretically be able cycle the key on/off a couple times too restore system pressure before cranking.

[Bitsyncmaster]

If it's a hot start problem, priming does not cure it. The hot start gets vapor bubbles in the injector lines which prevents the injectors from spaying on engine start. What gets it clear is getting the engine started and that vacuum is able to get the lines clear eventually.

Holding rest pressure until the engine cools prevents the bubbles from forming.

[David T]

If it's a hot start problem, priming does not cure it. The hot start gets vapor bubbles in the injector lines which prevents the injectors from spaying on engine start. What gets it clear is getting the engine started and that vacuum is able to get the lines clear eventually.

Holding rest pressure until the engine cools prevents the bubbles from forming.

Rest pressure is so the injectors have enough pressure to immediately start spraying fuel. When warm-hot the CSV won't activate so you are starting right on the injectors. When cold you do not need rest pressure, the CSV provides enough fuel to get the motor started and running till the fuel pump can get up enough pressure to squirt the injectors. Any bubbles from vapor lock will be squished once you get pressure up so that is a minor issue.
David Teitelbaum

[Ron]

The fuel smell may be a leak allowing the rest pressure to drop allowing vapor lock... I don't think you would be smelling a leaky injector, but that might explain the other symptoms...allows pressure to drop when hot resulting in vapor lock when it's hot, floods/fowls a cylinder making it hard to start when cold...and even after cooling 6 hous...
??

Rest pressure is to prevent vaporization=>vapor lock...not immediate fuel delivery on a hot/warm engine -- nothing to do with the CSV, remember it takes less fuel to start than a cold engine does...

[stevedmc]

Put a carb on it. Drew was having K-Jet problems and he has been very happy with his conversion.

[Ron]

Welcome back (in style) Steve!

[ccurzio]

Here's a question. Where would I put one of these?

http://www.actron.com/product_detail.php?pid=16173

[stevedmc]

Here's a question. Where would I put one of these?

http://www.actron.com/product_detail.php?pid=16173

You wouldn't need one.

[Chris4099]

Here's a question. Where would I put one of these?

http://www.actron.com/product_detail.php?pid=16173

That wouldn't work well (could probably be adapted to measure rest pressure only). You want one designed for K-Jet that allows it to function in-line. This way you can measure primary pressure and the control pressure. Something like this:
http://www.tooldiscounter.com/ItemDisplay.cfm?lookup=SAG33800&source=froogle&kw=SAG33800

[ccurzio]

That wouldn't work well (could probably be adapted to measure rest pressure only). You want one designed for K-Jet that allows it to function in-line. This way you can measure primary pressure and the control pressure.

Unless my understanding is incorrect, the whole point of all of the adapters that come with it is so you CAN test in-line. Note the adapter on the lower-left. Rubber fuel line goes in both ends.

I just need to find the best place to put it.

[Chris4099]

About the only place I can think of where you can put that adapter is up front by the fuel pump as it appears its meant to work with rubber fuel line (which isn't used in the engine bay). You could probably use the banjo adapter at the distributor if you get a longer hollow bolt. The nice thing about the one I listed is it can measure both control and primary pressures with a flip of a switch. No need to tap into multiple fuel lines. Also, it has all the adapters you need. You'll just want a few extra copper washers to replace the ones at the CPR.

The correct gauge is also only $11 more, so well worth it when you consider you get easier hookup without having to adapt a schrader valve.

[ccurzio]

Rubber fuel lines aren't used in the engine bay? I'm staring at them right now. The line running to the fuel distributor is rubber and every one if the six lines coming off of it are also rubber.

The point behind not wanting to buy the "correct" gauge is because I already own the one I posted.

[dmc6960]

Rubber fuel lines aren't used in the engine bay? I'm staring at them right now. The line running to the fuel distributor is rubber and every one if the six lines coming off of it are also rubber.

The problem is, only the "outside" is rubber. You can not cut and splice these lines like your thinking you can.

[Chris4099]

You're looking at a rubber protector. The actual line inside there is plastic.

If you still have the banjo adapter, you can probably connect it to the line coming from the filter. You'll just need another bolt and some additional washers. Of course you now added a point of failure for a fuel leak and you are limited to measuring primary pressure only. That's why I recommend the proper gauge.

[ccurzio]

Ah okay, that makes sense. Well shit, I'd rather not have a completely useless gauge.

[82DMC12]

If you are going to buy/own a fuel pressure gauge to use on a D, it has to be one like the second type posted, one that has a diverter valve to switch between measuring primary and control pressures. All other gauges are really kind of useless. They don't easily answer the questions you have.

Andy

[Ron]

From another thread-

Hmm... I'm having apparent rest pressure problems myself and I also have the combo unit.

I'm going to start by replacing the fuel accumulator, but I really really hope it's not my pump.

I suggest you ride up and put my pressure tester on your car to end a lot of the mystery first...

[ccurzio]

From another thread-


I suggest you ride up and put my pressure tester on your car to end a lot of the mystery first...

Name a time and I would be most grateful. :)

[Ron]

Basically anytime...I have to play moderator for a fire meeting this evening, but I'm usually around here somewhere...tomorrow anytime if you want. Whenever, just let me know.

[nullset]

I have the K-Jet pressure gauge. I can bring it to the OTPDOC lunch if you'd like to borrow it.....

Also, Sean was selling one. I don't know if it sold or not.

--buddy

[ccurzio]

Basically anytime...I have to play moderator for a fire meeting this evening, but I'm usually around here somewhere...tomorrow anytime if you want. Whenever, just let me know.

Tomorrow sounds good. I'd like to take you up on that. Thanks.


I have the K-Jet pressure gauge. I can bring it to the OTPDOC lunch if you'd like to borrow it.....

Also, Sean was selling one. I don't know if it sold or not.

--buddy
I didn't catch that he was selling one. I'll have to check with him to see if he still has it.

[Dangermouse]

I think he said on his thread that it was sold.

[ccurzio]

It is indeed sold. Ron and I also narrowed the problem right down to the pump unit.

[ccurzio]

Man, I have said this several times before and it bears mentioning again. Out of all the DMC vendors with whom I have had dealings - Dave and Julee at DMCMW, Toby and Misty at DMCNW, and of course the entire staff at DMCH (Particularly James and Stephen) - every last one of them has been an absolute pleasure to work with. Without exception they have all been extremely generous with their time and knowledge, and the customer support I've received through all of them has been absolutely outstanding.

Not once have I ever had a negative experience in any of my dealings with any of them. You will find their service and support to be second to none, so as I've said in the past, I love to support these guys because they support us.

So count this as another oft-repeated thank you from me to the entire DMC team. :)