The saga of VIN 4159, engine problems, any ideas?

[rothsean]

So I get the distributor fixed last week. Changed oil today and adjusted timing so that it is perfect. I decide to take the car on my errands today. The first 20 miles were perfect. After 20 miles I was idling at the bank drive thru teller and the idle got a little rough. When I went to leave I noticed that the car was struggling to gain speed and it was jerking back and forth a little as I tried to accelerate from stop to 25mph or so. It felt like occasional roughness and missing a cylinder. When I got above 3000 RPM the engine ran smooth. I drove home (20 miles to go) and every stop light or stop sign was a headache. The car quit a few times and when I got it started it was a struggle to get up to 20-30 mph. It was running very rough and the only way I managed to move the car from a stop was to get the RPM high with the clutch pressed and slip the clutch in slowly to 1st gear. Once I did that and babied it up to 30mph the engine was ok, once again 3000 RPM or higher.

I finally got it home.

I forgot to mention, 2 times that it quit I had to wait for the car to cool 5-10 minutes before it would start again. Most of the time while driving I smelled a strong scent of gas.


Any ideas? Should I check anything in particular? I am putting new spark plugs in just because I was planning to anyways.

[Jonathan]

Check that the spark plug wires are clipped in completely and the little depressions are not wet, especially if you just gave it an aggressive car wash with the power hose.

[jawn101]

So I get the distributor fixed last week. Changed oil today and adjusted timing so that it is perfect. I decide to take the car on my errands today. The first 20 miles were perfect. After 20 miles I was idling at the bank drive thru teller and the idle got a little rough. When I went to leave I noticed that the car was struggling to gain speed and it was jerking back and forth a little as I tried to accelerate from stop to 25mph or so. It felt like occasional roughness and missing a cylinder. When I got above 3000 RPM the engine ran smooth. I drove home (20 miles to go) and every stop light or stop sign was a headache. The car quit a few times and when I got it started it was a struggle to get up to 20-30 mph. It was running very rough and the only way I managed to move the car from a stop was to get the RPM high with the clutch pressed and slip the clutch in slowly to 1st gear. Once I did that and babied it up to 30mph the engine was ok, once again 3000 RPM or higher.

I finally got it home.

I forgot to mention, 2 times that it quit I had to wait for the car to cool 5-10 minutes before it would start again. Most of the time while driving I smelled a strong scent of gas.


Any ideas? Should I check anything in particular? I am putting new spark plugs in just because I was planning to anyways.

Was the idle normal during these "jerking" periods? Or was it higher than usual?

[rothsean]

Was the idle normal during these "jerking" periods? Or was it higher than usual?

Idle seemed to be normal, in the 800 RPM range.

If I was waiting at a stop light I would hold the engine around 1500RPM or so, just so it would not die. It died 2 times when I was decelerating towards a stop, around 20 mph and stick in neutral.

[DavidProehl]

Do you have an original fuel pickup line? If so perhaps it is collapsing in the Texas heat. That would be consistant with your first 20 miles being smooth and trouble free. If this regularly happens after the car/gas warms up that would be a key indicator.

[jawn101]

Do you have an original fuel pickup line? If so perhaps it is collapsing in the Texas heat. That would be consistant with your first 20 miles being smooth and trouble free. If this regularly happens after the car/gas warms up that would be a key indicator.

Good call David. Definitely worth checking.

[rothsean]

Do you have an original fuel pickup line? If so perhaps it is collapsing in the Texas heat. That would be consistant with your first 20 miles being smooth and trouble free. If this regularly happens after the car/gas warms up that would be a key indicator.

Good idea. I am going to change out the fuel pump unit today, I just got the new one from DMCH. Are you referring the the fuel line in the tank or from the pump going to motor?

[jawn101]

Good idea. I am going to change out the fuel pump unit today, I just got the new one from DMCH. Are you referring the the fuel line in the tank or from the pump going to motor?

Pickup inside the tank to the pump is the one that collapses. Be sure you clean your tank while you're in there.

[DavidProehl]

When looking at the line, check for signs that it is getting gooy or crumbling. Mine was starting to tear a little. The original fuel pick up lines are notoriously bad for working well until they get warm. I even had similar problems with a new replacement line, until I put a spring into it to hold it open. This write up (http://www.dmcnews.com/Techsection/fuelhose.htm) explains what spring to use and how to install (assuming this is your issue).

[jawn101]

But if you're installing the new integrated pump/sender combo from DMCH, you don't need a spring, or a pickup line, or a baffle, or any of that foolishness :) The new pump sounds like such a great idea... I secretly can't wait until I need one :shhh:

Hope this is your issue. It sure sounds like it and you already have the parts on hand to fix it, so that's great. Let us know how it goes.

[dmc6960]

(assuming this is your issue)

Which if it is, will be remedied by the installation of the new all-in-one fuel pump, baffle, and level sender. That is what you have when you said you had Houston's new one, right? Dont skimp on cleaning the tank.

But you already know all of this due to post #10...

[DavidProehl]

But if you're installing the new integrated pump/sender combo from DMCH, you don't need a spring, or a pickup line, or a baffle, or any of that foolishness :) The new pump sounds like such a great idea... I secretly can't wait until I need one :shhh:

Hope this is your issue. It sure sounds like it and you already have the parts on hand to fix it, so that's great. Let us know how it goes.

Ah! Yes. Somehow I missed that it was the new combo unit, I was thinking it was a new pump only. Problem solved. Much better than messing around with pickup lines.

[sdg3205]

Food for thought:

I had this issue and chased it for 6 months. Drove me crazy. Did the spring trick, changed the filter, double checked all the injectors etc etc. basically went through the entire fuel system time and time again. The weird part was that it would stumble up to 3000 rpm then take off after that, which was "weird" for a fuel problem. Eventually after the stumbling got worse over the course of a drive the car would stall and id have to wait 10 minutes until it would start again.

Just as I was about to drive it off a cliff toby asked if I checked the coil. I had not, and sure enough the coil was toast. $36 later my car runs beautifully and never stumbled or stalled again. Turns out a bad coil overheats and drops in voltage. The longer the drive, the hotter it gets and the more stumbling you get until complete stall.

Something to consider.

Cheers,

[Bitsyncmaster]

If you have the cover over the coil, try removing that cover and see if it helps. I also agree that a fuel pump problem should show up more at high RPM because the engine need more fuel.

[rothsean]

I did end up replacing the fuel pump with the new all-in-one unit. I drove it around for about 400 miles or so. I thought all was well until last week when I took it out for a long drive. I drove it for 35 miles on the highway and when I got off and stopped at a light the car started to idle rough and felt like it wanted to quit every 5 or 6 seconds. I then headed home and the idle got worse at every stop. The last 15 miles the car started to starve for power and jerk when I would step on the gas during acceleration.

I got annoyed and took it to DMCH, that is where it is now. I am told that there are vacuum leaks around the injectors, spark plug wires are bad. In addition, the new fuel pump unit is not maintaining rest pressure, so they are replacing that for free since it is only a month old.

I am thinking of having them do the work on the car, including the 30,000 mile service.

Any recommendations??

[ccurzio]

In addition, the new fuel pump unit is not maintaining rest pressure

How was this determined?

[rothsean]

How was this determined?

They pressurized the fuel system and noticed that it was loosing rest. They isolated the fuel pump by crimping the lines and once the fuel pump was out of the picture the system maintained pressure.

[ccurzio]

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.

[ccurzio]

Welp, it's definitely my pump. First test was to test the system as a whole, and it was definitely losing rest pressure.

Hooked the pressure gauge directly to the pump's output port and cycled power. With power on it jumped to high 90s PSI, but once power was cut the pressure dipped rather quickly to around 45 PSI. It continued to drop, and after roughly five minutes it had fallen to around 17 PSI.

This makes me sad. Aside from the warranty I really really like the DMCH combo unit. I hope it's not a design flaw. :(

[jawn101]

Welp, it's definitely my pump. First test was to test the system as a whole, and it was definitely losing rest pressure.

Hooked the pressure gauge directly to the pump's output port and cycled power. With power on it jumped to high 90s PSI, but once power was cut the pressure dipped rather quickly to around 45 PSI. It continued to drop, and after roughly five minutes it had fallen to around 17 PSI.

This makes me sad. Aside from the warranty I really really like the DMCH combo unit. I hope it's not a design flaw. :(

2 in such a short time is interesting but not enough to call a trend... yet. Will they be replacing it for you?

[ccurzio]

2 in such a short time is interesting but not enough to call a trend... yet. Will they be replacing it for you?

I don't see why they wouldn't. The thing is broken and I'm still within the warranty period.

I haven't contacted them yet since everything was put back together roughly 45 minutes ago, and they're closed for the weekend.

[jawn101]

[
I don't see why they wouldn't. The thing is broken and I'm still within the warranty period.

I haven't contacted them yet since everything was put back together roughly 45 minutes ago, and they're closed for the weekend.

Bummer. Best of luck though, I'm sure they'll do what they can to make it good for you! Hey, at least you found your problem.

[Bitsyncmaster]

Welp, it's definitely my pump. First test was to test the system as a whole, and it was definitely losing rest pressure.

Hooked the pressure gauge directly to the pump's output port and cycled power. With power on it jumped to high 90s PSI, but once power was cut the pressure dipped rather quickly to around 45 PSI. It continued to drop, and after roughly five minutes it had fallen to around 17 PSI.

This makes me sad. Aside from the warranty I really really like the DMCH combo unit. I hope it's not a design flaw. :(

Was that test without the accumulator attached? If just attached to the pump that may be a normal leak down rate for all pumps. Your gauge setup would also need to be perfect no leak attachments (pipe joint would need sealer).

[ccurzio]

Was that test without the accumulator attached? If just attached to the pump that may be a normal leak down rate for all pumps. Your gauge setup would also need to be perfect no leak attachments (pipe joint would need sealer).

Four tests were performed: operating pressure for the entire system, rest pressure for the entire system, operating pressure directly on the pump, and rest pressure directly on the pump. For the pump tests, the gauge was hooked directly to the pump itself with nothing else attached. The first two tests confirmed that the entire system is losing rest pressure, and the second two tests showed the pump itself could not maintain standard rest pressure when nothing else was hooked up.

The workshop manual says the following:
- Control Pressure must be between 71 and 79 PSI. My system maintains 75 PSI while running. (That's why the car runs fine once it gets started.)
- The system is supposed to hold rest pressure at 47 PSI, and be able to maintain a rest pressure of at least 25 PSI after ten minutes. My system dropped straight to 45 immediately at power-off (also normal), and then fell to 0 PSI in less than ten minutes.

After doing these two tests is when the gauge was hooked directly to the pump itself. Even if there's a leak somewhere else in the system, 17 PSI after five minutes is still way out of spec for that pump.

[Ron]

Was that test without the accumulator attached? If just attached to the pump that may be a normal leak down rate for all pumps. Your gauge setup would also need to be perfect no leak attachments (pipe joint would need sealer).

We hooked the gauge straight to the output port. The pump kit does not have a seperate replacement check valve...you add quick connectors to the existing lines and that's it for the pluming. (First one I've seen in person...nice setup!) So the pump is bad or somebody dropped the ball on the kit...

[Bitsyncmaster]

We hooked the gauge straight to the output port. The pump kit does not have a seperate replacement check valve...you add quick connectors to the existing lines and that's it for the pluming. (First one I've seen in person...nice setup!) So the pump is bad or somebody dropped the ball on the kit...

I don't know what to expect doing a leak down test without the accumulator. I've been doing leak testing on my propane supply to the generator and wasted a lot of time with a cast bronze T that shows a leak when the volume is very small. Now testing the pump your air volume is only what is in the gauge line. These kind of minute volumes even with leaks so small they would not show up with leak detector.