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Water in the Fuel System: Clearing Injectors, Testing Spark and Cleaning the Fuel Tank

Repairs and Maintenance Blog

The DeLorean needs routine maintenance and the occasional, more significant refurbishing.  Beyond that there are also a number of customizations and upgrades to improve performance, reliability and functionality. 

Water in the Fuel System: Clearing Injectors, Testing Spark and Cleaning the Fuel Tank

Joe Angell

Somehow, water got into my fuel system.  Water causes the steel components to rust, and can destroy the fuel injectors, distributor, pump and other parts.  The prevailing theory is that the fuel pump boot and cover are rotting, which is allowing water to get in.  The high humidity and heat over the last few weeks may have caused water to condense on the bottom of the trunk and leak past the fuel pump boot and cover and into the tank.


This is not the first time I've had problems with water in my fuel system. 

Around 2004 I had a power loss problems when driving around Vermont.  I turned around and took it home, and after talking with DeLorean Motor Center (now DMC CA)  was able to determine that the fuel injectors were ruined by water in the gas.  After draining the gas and replacing the injectors, the car ran fine.

 Circa 2005 I got some bad gas.  I had driven from Vermont to Connecticut to visit my parents, stopping once for fuel along the way.  When I took the car out the next day, it worked fine until I tried to get back to my parents' house.  I experienced significant power loss, finally having to call a tow truck when I couldn't make it up a hill.  A few days of research (I didn't know much about working on cars at this time) revealed that there was a significant amount of water in the fuel, and that the fuel distributor was ruined.  This is how I learned how expensive fuel distributors are, although they seem to be a few hundred dollars less now than they were then.

These pictures are from draining the gas in 2005. 


I first noticed a problem one morning, when the car drove rough and had trouble getting over 3000 RPMs.  It cleared up after a few miles, and I was able to finish my errands and make it home without incident.   There was about half a tank of gas in the car at this time.

Later that day, I had to take a 30 minute drive and the symptoms returned.  I turned around after 15 minutes, but just before I made it home the engine cleared up, so I decided to still try to make my appointment.  On the way home I had the same issues again, and stayed in the slow lane of the highway just to be sure. 

Two weeks later I tried to take the car out once more, and I couldn't get over 1500 RPMs, with a top speed of maybe 20 MPH.  At this point I was down to less than 1/8 of a tank of gas.  I turned around after a quarter mile and took the practical car out instead; I'd have to wait until the next day to figure out what was going on.


My first problem was that I couldn't drive the car, which meant that I had to do the diagnosis in the condo parking lot.  They tend to frown on working on your car, but they're also pretty forgiving.  Still, I wanted to do as little as possible.  Ideally, I'd get the car running well enough to drive it to the garage I rent in Pawtucket, RI, but there was no way I'd make it the 20 miles with the car in its current condition.  I could tow it, but the garage sits right on the street with a moderate incline and a two inch lip -- there was no way the truck could drop it off in the garage, and no way I could push it in, and there's no place to mount a winch to tow it in.  This left me to do the work in the parking lot, or at least enough work to get it to the garage.

Testing Spark

First I wanted to check for spark.  I used an inductive timing light as an impromptu spark plug tester to confirm that I had spark on each cylinder (as well as an inline tester for three of the cylinders, until I remembered I had the timing light).   The ignition circuit appeared to be fine.

For the inductive timing light: 

  1. Remove the air box. 
  2. Clip the positive terminal of the tester to the battery post on the right side of the engine bay, and the negative side to the engine block.
  3. Start the car.
  4. Attach the timing light's inductive clip around a spark plug wire
  5. Hold down the button on the timing light.  Every time that cylinder fires, the light will flash.
  6. Repeat steps 3 and 4 for each cylinder. 

For the inline tester:  This is more difficult for #4 and #5 due to the cold start value, idle speed motor and other components blocking access; they may need to be unmounted and moved to get enough access.

    1. Remove the air box.
    2. Remove a spark plug wire from the engine block
    3. Connect the female end of the tester to the spark plug
    4. Connect the male end of the tester to the spark plug wire
    5. Start the car, or have someone crank it for you.  The light in the tester will flash each time the cylinder fires. 
    6. Repeat steps 1 through 4 for each spark plug. 

    Testing Primary Pressure


    While I was here, I also pressure tested the system.  I did this with an OTC Master Fuel Pressure Test Kit 6550, using adaptors 76 and 77.  It's simple enough to hook up.  I only did a primary pressure test, as this can be done with the car off.:

      1. Find the fuel line that runs from the top of the fuel distributor to the control pressure regulator (aka the warm-up regulator), and disconnect it at the CPR.
      2. One of the adaptors fits on the fuel line and goes into hose on the test kit like a banjo bolt would.
      3. The other adaptor screws into the CPR and connects to the other end of test kit host.
      4. Open the valve on the test kit's gauge
      5. Jump the RPM relay socket pins 37 and 80 to run the fuel pump

      Testing the CPR response requires running the engine until it warms up, and I didn't want to bother my neighbors with the loud engine noise on a project I wasn't supposed to be doing there anyway.  The primary pressure test gave me a reading of about 69 PSI.  That's a touch under the 70 to 72 PSI specced by the Workshop Manual, but it's close enough.

      These pictures show the results of the pressure test and the separated glass and water.  The video shows the poor spray patterns on the #2 and #3 injectors.

      Testing Injectors

      Next came fuel.  I then pulled all six injectors, placed them into cups and checked the spray pattern:

      1. Remove the clips from each injector.  You can use a flat-headed screwdriver, but a long-handled pick and hook set is much easier.  The #4 injector is a real PITA due to its location on the forward driver's side of the car, crowded by the idle air motorcold start valve and other components, which I had to at least unmount from the intake manifold so that I could get my pick on the clip and to remove the injector itself.  Even then it took me 20 minutes for just that injector.  If I had been in the garage, I would have removed those other components completely.
      2. Place the injectors into one or more clear glass test tubes, glasses, mason jars, etc.  Use the injector clips to secure it to the side of the container, and find a place to rest the container in the engine bay.  Don't use plastic, as gas can dissolve some plastics.
      3. Remove the RPM relay from the fuse/relay area and jump pins 87 and 30.  This will cause the fuel pump to run continuously until disconnected.  A jumper can be easily made with two quick-disconnect blade-style connectors, a short piece of wire and a crimp tool from any auto-parts store.
      4. Push down on the air deflector plate on the mixture control unit until the injectors begin to fire (this can be see in the video below).  Ideally, you'll see a fine mist of fuel from each injector, but you may see some jets or other not-quite perfect spray.  If you see significant defects (like fuel only coming out of part of the injector) or drips instead of or in addition to spray, you might have a problem.  It's important to note that this is a crude injector test only, and just gives a ballpark of the quality of the injectors.

      The spray pattern wasn't very good; all of them had less-than-ideal spray, although I'm told that this is not that uncommon -- it seems you only really get the ideal spray pattern with completely new injectors.   However, I was seeing cases where more than half of an injector wasn't spraying, while other injectors were dripping after they had closed. 

      Testing the injectors gave me few ounces of gas to examine.  This gas did not look right.  After letting it sit for a bit, the heavier water separated out and was clearly visible sitting at the bottom of the glass. 


      After some more discussion on DMCTalk, it was generally agreed that I had water in the gas.  Dave Tietelbaum graciously cleaned my fuel injectors for me.  When taking the injectors out of the car, I found it easier to remove the fuel lines from the distributor first, and then remove the injectors from the lines.  Dave said mine are the worst he'd ever seen.  Five of them were able to be cleaned and are usable, but unfortunately one was unsalvageable, and I ordered a replacement from DeLorean Midwest, along with new injector boots (mine were dried and hard) and -- just in case -- two extra M8 banjo bolts, as I have a habit of breaking them.  I also ordered two bags of M8 copper sealing washers from McMaster-Carr, since they are not reusable.  At Home Depot I picked up a gas can for the bad fuel, a second gas can for clean fuel, and a pump siphon to drain the bad fuel from the tank.

      It was strongly recommended that I clean the tank before I try to start the car again.  I was very wary of this, because I'd have to do it in the parking lot.  Luckily, the tank is under the trunk, so it should have looked like I was just cleaning out the trunk.  It was also recommended to not use the fuel pump to drain the tank, and instead remove the fuel pump and siphon out the gas.  After that, the tank can be wiped clean with rags.  I decided to at least get the water out of the tank while in the parking lot, then drive it to the garage for a more thorough cleaning and to replace the fuel filter.

      Repairs and Cleaning

      I re-attached the fuel injectors to the fuel lines with new copper washers on the bench.  I bought a new torque wrench that measured in inch-pounds sot hat I could do the recommended 7-9 ft lbs of torque and not break the banjo bolts as I've done in the past.  This is quite a small amount of torque, and it's very easy to over-tighten them.  I wound up spending far too much on this at Home Depot (~$70); you can get them for half that or less on Amazon, but I was in a hurry and needed it that day.

      After getting the engine bay together, I pulled out the fuel pump to clean the tank:

      1. If you have a strut bar in the trunk, remove it with a 17mm socket.
      2. Remove the carpet.
      3. Remove the board under the carpet, if you have it.
      4. Remove the spare tire.
      5. Remove the nine (9) screws holding the fuel pump access panel down.   A power screwdriver is very helpful here.  A number of the screws in mine were stripped.
      6. Disconnect the fuel pump electrical connector.
      7. Remove the clamp holding the fuel pump boot in place with a 6mm socket.
      8. Pull back the fuel pump cover .  The plastic covering the lines flaked off in my hands.
      9. Lift the fuel pump boot to pull the fuel pump out of the tank.  Be careful of the still-connected fuel hoses, both above the fuel pump and inside the tank.

      When I pulled the cover off of the pump, I saw that it was completely filled with water, and everything within there was rusted.  Luckily I didn't have to remove the fuel fittings yet, but this seemed to be the source of my problem:  it's likely that water was seeping into the pump from above, and that the cover wasn't doing its job.

      With the fuel pump out, I was able to drain the tank.  This is as simple as you'd expect: 

      1. Place the inlet side of the pump siphon into the tank.  I couldn't get my hose to stay put, so I wound up duct taping it to a long pry bar.  Be aware that duct tape adhesive very quickly degrades in gasoline, much faster than I had expected.  I had to re-tape it a couple times.
      2. Place an empty gas can in the trunk to collect the gas
      3. Place the outlet side of the pump into the gas can.  Again I had to duct tape it in place so that it wouldn't fall out
      4. Pump until the tank is as empty as you can get it.  Note that you don't want to pump to fast; a couple of times there was enough pressure that the inlet or outlet hose would pop out of the pump, spilling fuel in the trunk. 
      5. Once empty, use rags to sop up any remaining fuel from the tank.

      That was about all I did to clean the tank for now.  A thorough cleaning would have involved removing the baffle and cleaning the acetone, but my goal from the moment was just to get the bad gas out.  My tank already looked quite clean,, and a full cleaning would come when I replaced the rusted fuel pump and filter.  Mind you, I'm not sure that the pump needed to be replaced, but I figured it was better to do it now than to wait until more water ruined other fuel system components.

      These pictures show the inside of the gas tank after my very simple cleaning -- again, my goal was mostly to remove the water, not really clean the tank.  Still, it looks pretty clean already.

      After putting the pump back in and sealing everything up, I added 2.5 gallons of new gas and turned the key from "accessory" and "run" a few times to prime the fuel system.  Each time the key is turned to "run", the pump runs for a few seconds.  This didn't help as much as I'd hoped, though; it took about ten minutes to get the car started.  I even jumped the RPM relay directly to try to get the system primed faster.

      Once it finally started, I got a cloud of white smoke from the exhaust.  After a bit of a  struggling, the engine stabilized and sounded pretty much fine.   I had no misfirings anymore, and I was able to easily rev the engine to high RPMs without any problems.  I took it for a quick run down the street, only about a mile or so, and everything seemed fine, although I thought I noticed some slight hesitation and a misfire or two. 

      Not Quite...

      The next morning I took it out to get some gas.  While it seemed to run fine on my nice, flat, low-speed-limit road, as soon as I turned onto the next street and started going up a hill the car started misfiring again, including some popping noises from the exhaust.

      I never made it to the gas station; i turned around and came home, rather than risk driving only 20-30 MPH on a 45 MPH road.  I pulled the spark plugs to see if they were the problem.  #4 and #5 were fairly blackened; odd, since these a little over a year old.  I cleaned them off with a wire brush and some sandpaper, but when I put them back in the engine I had the same issues.

      The good news is that the car is running well enough that I think I can get it into the garage, once it is towed there.  The garage has a steep but short driveway (really, it just sits right in front of a side walk) -- too short for the tow truck to drop it in the garage. Worse, there's a two inch lip between the driveway and the garage.  I normally drive up on boards, and I still scrape the bottom of  the car. I'm thinking that the car is working well enough at the moment that I can at least back up to the lip, and then I can jack it up and put boards under the tires to raise them up over the lip itself.  Once in the garage I should have a lot more flexibility with repairs.

      Clean Up

        The next question I had was, what to do with the bad gas and rags? 

        For the rags, they had dried out pretty well while they were lying in the sun as I worked on the tank.  Gas/oil rags can spontaneously combust, so they need to be disposed of properly.  To do so I followed some instructions I found online:  I put them into a paint can, filled it with water, and stored it under my deck for the time being.   You're supposed to also add an oil breakdown detergent, but it's not clear to me where to get that.  Now I'm supposed to wait for a city-sponsored hazardous waste day to get rid of them.

        For the can full of bad gas... I'm still figuring that out.   Right now it's sitting under my deck, along with the can of rags.




        • Socket set
        • Spark plug socket
        • Socket extensions
        • Flathead screwdriver and allen wrench set to loosen hose clamps when moving the CPR and idle air motor to get better access to the #4 injector.
        • Philips screwdriver to remove the fuel pump access cover
        • Power screwdriver, which makes anything with screws much easier to deal with
        • Inch-pound range torque wrench to torque the banjo bolts on the fuel lines

        Engine fuel and spark tests

        Fuel tank and pump

        • 2.5 gallon gas can with fresh gas
        • 5 gallon gas can to drain fuel into
        • Pump siphon to drain the fuel from the tank into the gas can
        • Rags or paper towels to clean the tank