If you own, plan to own, and want to enjoy driving your old CIS fuel-injected Mercedes, Kent highly recommends you learn to do a full fuel system flow and pressure test. This can tell you if you have a weak fuel pump, a failed check valve or valves, a plugged fuel filter, a problem with the fuel distributor, leaking fuel injectors, a malfunctioning warm-up regulator (K-jetronic) or malfunctioning EHA valve (KE-jetronic), etc. With this "short" kit and a fuel pressure test kit that you can buy on Amazon, you can build your own tester in about 30 minutes that is reliable and accurate. Watch the YouTube video below for a full description of what is required.
Product Details
The kit includes the following:
- Quality accurate liquid filled 160 psi gauge with male 1/4 inch NPT threads.
- Brass adapter from 1/4 NPT female threads to 1/8 NPT male threads ( to adapt the gauge to many different testers )
- CIS-specific machined short fitting that does not leak
- Five small sealing rings for threaded attachments to prevent pressure fuel leaks
- Fuel pump relay jumper wire to get pumps running while the engine is off.
- 14mm super thin combination wrench to ease fitting installation on the fuel distributor
- One 20-minute video instruction on how to inspect,modify, and assemble your testing using this kit and one purchased online.
PLEASE NOTE: NO OTHER INSTRUCTIONS on hooking up the tester to your engine and reading results are included. If you are unfamiliar with how to do this, video instructions are available for purchase separately below. You can choose to buy our COMBO kit which includes all 6 training videos. See the related products below.
Here, you can see how the adapter fitting can be used to mount the new gauge just above the pressure release valve.
These are the fittings you will remove from the tester you purchase separately. You will not use the two small ones on the left, as they will leak in most cases. My assembly instructions included here will explain how the other fittings are used.
And here is where you can obtain the rest of the necessary components. Amazon is the best source (as of March 2024)for the generic fuel pressure you will need. There are 3 or 4 different brands in a very large red case. Even if the tester does not say Bosch CIS it will work if it has the hose arrangement with the valve as shown below and as explained in the video above. It should cost between $50 and $70. If it does not include this hose arrangement, then you do not have the correct tester.
Here is a closeup of the tester with the lid open. Notice the wide range of hoses and fittings most of which you will not need for testing Bosch CIS fuel injection.
Go to Amazon.com and put "fuel injection tester" in the search box. Look specifically for a tester that looks just like the picture above!
Here is what the tester will look like when it is all assembled.
Related Products:
Bosch CIS Fuel Injection Pressure Tester w/ Extras
If you own or are restoring a CIS fuel-injected Mercedes, a pressure tester is a must-have! This complete kit will allow you to do it yourself with complete instructions. Why buy a tester that you do not know how to hook up and may not even be accurate?
Bosch CIS Training Series 1: What’s Needed to Test K-Jet and KE-Jet Fuel Pressure
This video will help you decide if you want to try to do a fuel pressure test yourself. It is a fairly simple DIY job but will all the confusion and misinformation on the internet; one would believe it is a complicated process that is hard to understand.
Bosch CIS Training Series 2: Options to Get Fuel Pumps to Run with Engine Off
To do proper system testing on CIS fuel injection, you must find a way to get the fuel pump or fuel pumps to run continuously without the engine running. This can not be done by just using the ignition key. In this 15-minute training video, Kent will show the options available to do this.
Bosch CIS Training Series 3: How to Do Preliminary Fuel Flow and FD Leak Tests
There are a few factory recommend procedures and tests you should do before you do an actual pressure test on a CIS fuel-injected engine. In this 20-minute training video, Kent will walk you through these procedures step-by-step.
Bosch CIS Training Series 4: How to Hook Up and Test K-Jetronic Fuel Pressure
This video is specific to K- jetronic fuel-injected engines from 1976 to 1985. This includes the 350, 450, and 280 engines in the R107, W116, W123, and early W126 gas Mercedes. In this 29-minute video. Kent will show you how to hook up the gauge, run the fuel pumps, and complete the test.
Bosch CIS Training Series 5: How to Hook Up and Test KE-Jetronic Fuel Pressure
In this video, you will see how the gauges are hooked up to a 560SL and how the pressures are read. The length of this 30-minute shows the detail Kent has put into filming all the critical components of doing a KE-Jetronic fuel system pressure test.
Bosch CIS Training Series 6: Finding Follow-up Information to Help Interpret Test Results
After completing the pressure test on your CIS engine, you discover a problem. But how can you find out how to isolate and fix it? This is going to require some research on your part. Start by learning how the system works and how each component plays a part.
1976 to 1993 C.I.S Fuel Injection 6-Part Video Training Seminar
It has been over 30 years since the last Mercedes with Bosch C.I.S. fuel injection was manufactured. If you own a 1976 to 1993 Mercedes gas engine with this type of fuel injection, you may have difficulty finding someone to work on your car. In some parts of the country, it may be impossible.
K-jetronic Warm Up Regulator Cold Start Modification Kit w/ Video Instructions
Before you make this modification you should be very familiar with the function of the WUR and how its pressure adjustements affect the performance of the K-Jetronic fuel injection systems. The tools and supplies offered in this kit will allow you to modify your warm up regulator at home and it y
How to Test the EHA Valve on Bosch KE-Jetronic Fuel Injected Engines - On Demand Video
In this 13-minute CIS training video, Kent will walk you through the steps recommended by Mercedes Benz to fully test the operation of the EHA valve on 1984 to 1993 4, 6, and 8-cylinder engines with KE-jetronic fuel injection.
Super Thin 14mm Combination Wrench for CIS Pressure Tester Fittings
When pressure testing your KE-jetronic fuel injection, you may find you need a really thin wrench to install the small fitting on the right side bottom of the fuel distributor.
KE-Jetronic Fuel Injection Troubleshooting Multimeter w/ Special Attachments
This high-quality meter can test all types of automotive electrical circuits, but Kent has discovered it is particularly well suited for testing Bosch KE jetronic fuel injection components on those CIS models from 1984 to 1993.